NEET (UG) · 2018

NEET 2018, question by question

Which chapter each question came from, how the paper was spread, and how to solve each one. Keep the official paper open beside this page.

Sit this paper free All years, chapter-wise

Summary

The heaviest chapters in each subject, and how the questions were spread by level. One year is not a forecast.

Physics
45 Q
1. Optics5
2. Motion of System of Particles and Rigid Body4
3. Thermodynamics3
30 easy · 15 medium · 0 hard
Chemistry
45 Q
1. Chemical Bonding and Molecular Structure5
2. p-Block Elements3
3. Alcohols, Phenols and Ethers3
30 easy · 15 medium · 0 hard
Botany
54 Q
1. Molecular Basis of Inheritance6
2. Biological Classification5
3. Sexual Reproduction in Flowering Plants4
42 easy · 12 medium · 0 hard
Zoology
36 Q
1. Biotechnology and its Applications4
2. Human Reproduction4
3. Breathing and Exchange of Gases3
27 easy · 8 medium · 1 hard

Chapters

Every chapter asked, and the NCERT chapters to read for it.

Molecular Basis of Inheritance6
Class 12: Molecular Basis of Inheritance
Biological Classification5
Class 11: Biological Classification
Sexual Reproduction in Flowering Plants4
Class 12: Sexual Reproduction in Flowering Plants
Principles of Inheritance and Variation4
Class 12: Principles of Inheritance and Variation
Organisms and Populations4
Class 12: Organisms and Populations
Environmental Issues4
No matching NCERT chapter
Cell: The Unit of Life4
Class 11: Cell: The Unit of Life
Anatomy of Flowering Plants4
Class 11: Anatomy of Flowering Plants
Plant Kingdom3
Class 11: Plant Kingdom
Photosynthesis in Higher Plants2
Class 11: Photosynthesis in Higher Plants
Mineral Nutrition2
No matching NCERT chapter
Respiration in Plants2
Class 11: Respiration in Plants
Reproduction in Organisms2
No matching NCERT chapter
Morphology of Flowering Plants2
Class 11: Morphology of Flowering Plants
Ecosystem1
Class 12: Ecosystem
Transport in Plants1
No matching NCERT chapter
Cell Cycle and Cell Division1
Class 11: Cell Cycle and Cell Division
The Living World1
Class 11: The Living World
Biodiversity and Conservation1
Class 12: Biodiversity and Conservation
Microbes in Human Welfare1
Class 12: Microbes in Human Welfare

Questions

Tap Explain on any question for a short summary and our full working.

Physics questions, each with its chapter and our explanation
Q	Chapter and topic	NCERT	Kind and level
1	ThermodynamicsThermodynamic processes	Class 11: Thermodynamics	Single correctEasy
A easy single correct question on thermodynamic processes, from Thermodynamics. NCERT: Class 11: Thermodynamics The graph of V against T is a straight line through the origin, so $V \propto T$: the pressure is constant and the change A → B is isobaric. For an isobaric change of n moles: work done by the gas $W = P\Delta V = nR\Delta T$. Heat absorbed $Q = nC_p\Delta T$, and for a monatomic gas $C_p = \frac{5}{2}R$, so $Q = \frac{5}{2}nR\Delta T$. $\frac{W}{Q} = \frac{nR\Delta T}{\frac{5}{2}nR\Delta T} = \frac{2}{5}$. Answer: (3).
2	Oscillations and WavesStanding waves and beats	Class 11: Oscillations; Class 11: Waves	Single correctEasy
A easy single correct question on standing waves and beats, from Oscillations and Waves. NCERT: Class 11: Oscillations; Class 11: Waves For a pipe closed at one end, the harmonics are $\frac{nv}{4L_c}$ with n odd; the third harmonic is $\frac{3v}{4L_c}$. For an open pipe, the fundamental is $\frac{v}{2L_o}$. Setting them equal: $\frac{v}{2L_o} = \frac{3v}{4L_c} \Rightarrow L_o = \frac{4L_c}{6} = \frac{2}{3}L_c = \frac{2}{3}\times20 = 13.3$ cm. The nearest option is 13·2 cm. Answer: (3).
3	Behaviour of Perfect Gas and Kinetic TheoryKinetic theory	Class 11: Kinetic Theory	Single correctMedium
A medium single correct question on kinetic theory, from Behaviour of Perfect Gas and Kinetic Theory. NCERT: Class 11: Kinetic Theory The molecules can escape when their rms speed equals the escape speed from the Earth, $v_e = 11.2$ km/s $= 1.12\times10^4$ m/s. $v_{rms} = \sqrt{\frac{3k_BT}{m}} = v_e \Rightarrow T = \frac{mv_e^2}{3k_B}$. $T = \frac{2.76\times10^{-26}\times(1.12\times10^4)^2}{3\times1.38\times10^{-23}} = \frac{2.76\times10^{-26}\times1.2544\times10^8}{4.14\times10^{-23}}$ $= \frac{3.462\times10^{-18}}{4.14\times10^{-23}} \approx 8.36\times10^4$ K. Answer: (2).
4	ThermodynamicsSecond law	Class 11: Thermodynamics	Single correctEasy
A easy single correct question on second law, from Thermodynamics. NCERT: Class 11: Thermodynamics An ideal (Carnot) engine has efficiency $\eta = 1 - \frac{T_2}{T_1}$ with absolute temperatures. $T_1 = 373$ K (boiling point), $T_2 = 273$ K (freezing point). $\eta = 1 - \frac{273}{373} = \frac{100}{373} = 0.268 = 26.8\%$. Answer: (3).
5	Current ElectricityResistivity	Class 12: Current Electricity	Single correctEasy
A easy single correct question on resistivity, from Current Electricity. NCERT: Class 12: Current Electricity $47$ k$\Omega = 47\times10^3\ \Omega$. First digit 4 → yellow; second digit 7 → violet; multiplier $10^3$ → orange. Tolerance: $\frac{4.7}{47} = 10\%$ → silver. Sequence: Yellow – Violet – Orange – Silver. Answer: (2).
6	Current ElectricityCells, emf and internal resistance	Class 12: Current Electricity	Single correctMedium
A medium single correct question on cells, emf and internal resistance, from Current Electricity. NCERT: Class 12: Current Electricity In series: $I = \frac{E}{nR + R} = \frac{E}{(n+1)R}$. In parallel the external resistance is $\frac{R}{n}$: $10I = \frac{E}{\frac{R}{n} + R} = \frac{nE}{(n+1)R}$. Dividing: $10 = \frac{nE/((n+1)R)}{E/((n+1)R)} = n$. So $n = 10$. Answer: (3).
7	Current ElectricityCells, emf and internal resistance	Class 12: Current Electricity	Single correctEasy
A easy single correct question on cells, emf and internal resistance, from Current Electricity. NCERT: Class 12: Current Electricity With n cells of emf E in series, the total emf is nE and the total internal resistance is nr. On short circuit the external resistance is zero, so $I = \frac{nE}{nr} = \frac{E}{r}$, which does not depend on n. The graph of I against n is a horizontal line. Answer: (3).
8	OpticsPolarisation	Class 12: Ray Optics and Optical Instruments; Class 12: Wave Optics	Single correctEasy
A easy single correct question on polarisation, from Optics. NCERT: Class 12: Ray Optics and Optical Instruments; Class 12: Wave Optics When the reflected and refracted rays are perpendicular, the angle of incidence is the Brewster angle: $i + r = 90^\circ$, and Snell's law $\sin i = \mu\sin r = \mu\cos i$ gives $\tan i = \mu$, i.e. $i = \tan^{-1}\mu$. So options (1) and (4) are wrong. At the Brewster angle the reflected light is completely plane polarised, with its electric vector perpendicular to the plane of incidence (the component in the plane of incidence is not reflected at all). Answer: (2).
9	OpticsInterference and diffraction	Class 12: Ray Optics and Optical Instruments; Class 12: Wave Optics	Single correctEasy
A easy single correct question on interference and diffraction, from Optics. NCERT: Class 12: Ray Optics and Optical Instruments; Class 12: Wave Optics The angular fringe width is $\theta = \frac{\lambda}{d}$, so for the same $\lambda$, $\theta \propto \frac{1}{d}$. $\frac{d_2}{d_1} = \frac{\theta_1}{\theta_2} = \frac{0.20}{0.21} \Rightarrow d_2 = 2\times\frac{0.20}{0.21} = 1.905$ mm $\approx 1.9$ mm. Answer: (2).
10	OpticsOptical instruments	Class 12: Ray Optics and Optical Instruments; Class 12: Wave Optics	Single correctEasy
A easy single correct question on optical instruments, from Optics. NCERT: Class 12: Ray Optics and Optical Instruments; Class 12: Wave Optics Angular magnification of a telescope (normal adjustment): $m = \frac{f_o}{f_e}$, so a large objective focal length gives large magnification. Resolving power is $\frac{D}{1.22\lambda}$ (the smallest resolvable angle is $\frac{1.22\lambda}{D}$), so a large objective diameter D gives high resolution. Answer: (1).
11	Atoms and NucleiBohr model	Class 12: Atoms; Class 12: Nuclei	Single correctEasy
A easy single correct question on bohr model, from Atoms and Nuclei. NCERT: Class 12: Atoms; Class 12: Nuclei In a Bohr orbit, $K = \frac{ke^2}{2r}$, $U = -\frac{ke^2}{r}$, so the total energy is $E = K + U = -\frac{ke^2}{2r} = -K$. $K : E = K : (-K) = 1 : -1$. Answer: (2).
12	Dual Nature of Matter and Radiationde Broglie wavelength	Class 12: Dual Nature of Radiation and Matter	Single correctMedium
A medium single correct question on de broglie wavelength, from Dual Nature of Matter and Radiation. NCERT: Class 12: Dual Nature of Radiation and Matter The force on the electron (charge $-e$) is $\vec{F} = -e\vec{E} = eE_0\hat{i}$, along its motion, so it speeds up with acceleration $a = \frac{eE_0}{m}$. $V(t) = V_0 + \frac{eE_0}{m}t = V_0\left(1 + \frac{eE_0}{mV_0}t\right)$. $\lambda = \frac{h}{mV}$, and $\lambda_0 = \frac{h}{mV_0}$, so $\lambda(t) = \frac{h}{mV_0\left(1 + \frac{eE_0}{mV_0}t\right)} = \frac{\lambda_0}{1 + \frac{eE_0}{mV_0}t}$. Answer: (3).
13	Atoms and NucleiRadioactivity	Class 12: Atoms; Class 12: Nuclei	Single correctEasy
A easy single correct question on radioactivity, from Atoms and Nuclei. NCERT: Class 12: Atoms; Class 12: Nuclei After 450 nuclei disintegrate, $600 - 450 = 150$ remain. $\frac{N}{N_0} = \frac{150}{600} = \frac{1}{4} = \left(\frac{1}{2}\right)^2$, so two half-lives have passed. $t = 2\times10 = 20$ minutes. Answer: (3).
14	Dual Nature of Matter and RadiationPhotoelectric effect	Class 12: Dual Nature of Radiation and Matter	Single correctEasy
A easy single correct question on photoelectric effect, from Dual Nature of Matter and Radiation. NCERT: Class 12: Dual Nature of Radiation and Matter Einstein's equation: $\frac{1}{2}mv_{max}^2 = h\nu - h\nu_0$. For $2\nu_0$: $\frac{1}{2}mv_1^2 = h\nu_0$. For $5\nu_0$: $\frac{1}{2}mv_2^2 = 4h\nu_0$. $\frac{v_1^2}{v_2^2} = \frac{1}{4} \Rightarrow v_1 : v_2 = 1 : 2$. Answer: (3).
15	Electronic DevicesSemiconductors	Class 12: Semiconductor Electronics: Materials, Devices and Simple Circuits	Single correctEasy
A easy single correct question on semiconductors, from Electronic Devices. NCERT: Class 12: Semiconductor Electronics: Materials, Devices and Simple Circuits Base circuit: $V_i = I_BR_B + V_{BE}$ with $V_{BE} = 0$: $I_B = \frac{20}{500\times10^3} = 4\times10^{-5}$ A $= 40\ \mu$A. Collector circuit: $20 = I_CR_C + V_{CE}$ with $V_{CE} = 0$: $I_C = \frac{20}{4\times10^3} = 5\times10^{-3}$ A $= 5$ mA. $\beta = \frac{I_C}{I_B} = \frac{5\times10^{-3}}{4\times10^{-5}} = 125$. Answer: (4).
16	Electronic Devicesp-n junction diode	Class 12: Semiconductor Electronics: Materials, Devices and Simple Circuits	Single correctEasy
A easy single correct question on p-n junction diode, from Electronic Devices. NCERT: Class 12: Semiconductor Electronics: Materials, Devices and Simple Circuits Heating creates more electron–hole pairs in the semiconductor. This changes the forward current for a given voltage (the barrier potential falls) and also increases the reverse saturation current (minority carriers increase). So both forward and reverse behaviour change: the whole V–I characteristic of the junction is affected. Answer: (4).
17	Electronic DevicesLogic gates	Class 12: Semiconductor Electronics: Materials, Devices and Simple Circuits	Single correctEasy
A easy single correct question on logic gates, from Electronic Devices. NCERT: Class 12: Semiconductor Electronics: Materials, Devices and Simple Circuits Trace the circuit: Upper AND gate: inputs A (direct) and B through a NOT gate, so its output is $A\cdot\overline{B}$. Lower AND gate: inputs A through a NOT gate and B (direct), so its output is $\overline{A}\cdot B$. The OR gate adds them: $Y = A\cdot\overline{B} + \overline{A}\cdot B$ (the XOR function). Answer: (2).
18	Electromagnetic WavesProperties of electromagnetic waves	Class 12: Electromagnetic Waves	Single correctEasy
A easy single correct question on properties of electromagnetic waves, from Electromagnetic Waves. NCERT: Class 12: Electromagnetic Waves In an em wave, $\vec{E}\times\vec{B}$ points along the direction of propagation. $\hat{j}\times\hat{B} = \hat{i}$ requires $\hat{B} = \hat{k}$, since $\hat{j}\times\hat{k} = \hat{i}$. So the magnetic field oscillates along the +z direction. Answer: (2).
19	OpticsTotal internal reflection and prisms	Class 12: Ray Optics and Optical Instruments; Class 12: Wave Optics	Single correctMedium
A medium single correct question on total internal reflection and prisms, from Optics. NCERT: Class 12: Ray Optics and Optical Instruments; Class 12: Wave Optics To retrace its path, the ray inside the prism must strike the silvered face normally. Then the angle of refraction at the first face equals the prism angle: $r = A = 30^\circ$ (since $r_1 + r_2 = A$ with $r_2 = 0$). Snell's law at the first face: $\sin i = \mu\sin r = \sqrt{2}\times\sin30^\circ = \frac{\sqrt{2}}{2} = \frac{1}{\sqrt{2}}$. $i = 45^\circ$. Answer: (2).
20	OpticsLenses and mirrors	Class 12: Ray Optics and Optical Instruments; Class 12: Wave Optics	Single correctMedium
A medium single correct question on lenses and mirrors, from Optics. NCERT: Class 12: Ray Optics and Optical Instruments; Class 12: Wave Optics Sign convention: distances in front of the mirror negative; $f = -15$ cm. First position, $u = -40$ cm: $\frac{1}{v} = \frac{1}{f} - \frac{1}{u} = -\frac{1}{15} + \frac{1}{40} = \frac{-8+3}{120} = -\frac{1}{24}$, so $v = -24$ cm. After moving 20 cm towards the mirror, $u = -20$ cm: $\frac{1}{v} = -\frac{1}{15} + \frac{1}{20} = \frac{-4+3}{60} = -\frac{1}{60}$, so $v = -60$ cm. The image moves from 24 cm to 60 cm in front of the mirror: 36 cm away from the mirror. Answer: (2).
21	Electromagnetic Induction and Alternating CurrentsSelf and mutual inductance	Class 12: Electromagnetic Induction; Class 12: Alternating Current	Single correctEasy
A easy single correct question on self and mutual inductance, from Electromagnetic Induction and Alternating Currents. NCERT: Class 12: Electromagnetic Induction; Class 12: Alternating Current $U = \frac{1}{2}LI^2 \Rightarrow L = \frac{2U}{I^2} = \frac{2\times25\times10^{-3}}{(60\times10^{-3})^2} = \frac{0.05}{3.6\times10^{-3}} = 13.89$ H. Answer: (4).
22	ElectrostaticsElectric field and potential	Class 12: Electric Charges and Fields; Class 12: Electrostatic Potential and Capacitance	Single correctEasy
A easy single correct question on electric field and potential, from Electrostatics. NCERT: Class 12: Electric Charges and Fields; Class 12: Electrostatic Potential and Capacitance With the field upward, the force on the electron $eE$ is downward; with the field reversed (downward), the force on the proton $eE$ is downward too. Both start from rest and move through h under a constant force of the same size (gravity is negligible beside the electric force on such particles, and in any case adds the same g to both). $h = \frac{1}{2}at^2$ with $a = \frac{eE}{m}$ gives $t = \sqrt{\frac{2hm}{eE}} \propto \sqrt{m}$. The electron is much lighter than the proton ($m_e \ll m_p$), so its time of fall is smaller. Answer: (3).
23	ElectrostaticsCapacitance	Class 12: Electric Charges and Fields; Class 12: Electrostatic Potential and Capacitance	Single correctMedium
A medium single correct question on capacitance, from Electrostatics. NCERT: Class 12: Electric Charges and Fields; Class 12: Electrostatic Potential and Capacitance One plate lies in the field of the other plate, $E' = \frac{\sigma}{2\varepsilon_0} = \frac{Q}{2\varepsilon_0A}$. Force on the plate carrying Q: $F = QE' = \frac{Q^2}{2\varepsilon_0A}$. For an isolated capacitor Q is fixed, so F does not contain the plate separation d: it is independent of the distance between the plates. Answer: (3).
24	Oscillations and WavesStanding waves and beats	Class 11: Oscillations; Class 11: Waves	Single correctEasy
A easy single correct question on standing waves and beats, from Oscillations and Waves. NCERT: Class 11: Oscillations; Class 11: Waves For a tube closed at one end, two successive resonance lengths differ by half a wavelength (the end correction cancels): $\frac{\lambda}{2} = 73 - 20 = 53$ cm, so $\lambda = 106$ cm $= 1.06$ m. $v = f\lambda = 320\times1.06 = 339.2$ m/s $\approx 339$ m/s. Answer: (2).
25	Oscillations and WavesSHM	Class 11: Oscillations; Class 11: Waves	Single correctEasy
A easy single correct question on shm, from Oscillations and Waves. NCERT: Class 11: Oscillations; Class 11: Waves In SHM, $\|a\| = \omega^2x$, so $\omega^2 = \frac{20}{5} = 4$ and $\omega = 2$ rad/s. $T = \frac{2\pi}{\omega} = \frac{2\pi}{2} = \pi$ s. Answer: (2).
26	Magnetic Effects of Current and MagnetismForce on moving charges and currents	Class 12: Moving Charges and Magnetism; Class 12: Magnetism and Matter	Single correctMedium
A medium single correct question on force on moving charges and currents, from Magnetic Effects of Current and Magnetism. NCERT: Class 12: Moving Charges and Magnetism; Class 12: Magnetism and Matter The rod is horizontal and the field is vertical, so the magnetic force on a length l is $BIl$, horizontal and perpendicular to the rod; the current is chosen so that this force pushes the rod towards the slope. Resolve along the incline (no friction). The component of the magnetic force up the incline must balance the component of the weight down the incline: $BIl\cos30^\circ = mg\sin30^\circ \Rightarrow I = \frac{(m/l)g\tan30^\circ}{B}$. With $\frac{m}{l} = 0.5$ kg/m, $g = 9.8$ m/s$^2$: $I = \frac{0.5\times9.8\times0.577}{0.25} = 11.32$ A. Answer: (4).
27	Magnetic Effects of Current and MagnetismMagnetic properties of materials	Class 12: Moving Charges and Magnetism; Class 12: Magnetism and Matter	Single correctMedium
A medium single correct question on magnetic properties of materials, from Magnetic Effects of Current and Magnetism. NCERT: Class 12: Moving Charges and Magnetism; Class 12: Magnetism and Matter The magnetic field itself only stores energy; it is set up and maintained by the current in the electromagnet. When the current is switched on and the rod moves, the energy given to the rod (its gain in gravitational potential energy) and the energy stored in the field are both supplied by the source that drives the current in the electromagnet. The lattice of the rod supplies no energy, and the force on a diamagnetic body is the magnetic force of the field, whose energy comes from the current source. Answer: (3).
28	Electromagnetic Induction and Alternating CurrentsAC circuits	Class 12: Electromagnetic Induction; Class 12: Alternating Current	Single correctMedium
A medium single correct question on ac circuits, from Electromagnetic Induction and Alternating Currents. NCERT: Class 12: Electromagnetic Induction; Class 12: Alternating Current $\omega = 314$ rad/s. $X_L = \omega L = 314\times0.02 = 6.28\ \Omega$; $X_C = \frac{1}{\omega C} = \frac{1}{314\times10^{-4}} = 31.85\ \Omega$. $Z = \sqrt{R^2 + (X_C - X_L)^2} = \sqrt{50^2 + 25.57^2} = \sqrt{2500 + 653.8} = 56.16\ \Omega$. $V_{rms} = \frac{10}{\sqrt{2}} = 7.07$ V, $I_{rms} = \frac{7.07}{56.16} = 0.126$ A. Power is lost only in the resistor: $P = I_{rms}^2R = (0.126)^2\times50 = 0.79$ W. Answer: (3).
29	Magnetic Effects of Current and MagnetismMoving coil galvanometer	Class 12: Moving Charges and Magnetism; Class 12: Magnetism and Matter	Single correctEasy
A easy single correct question on moving coil galvanometer, from Magnetic Effects of Current and Magnetism. NCERT: Class 12: Moving Charges and Magnetism; Class 12: Magnetism and Matter Current sensitivity $\frac{\theta}{I}$ and voltage sensitivity $\frac{\theta}{V} = \frac{\theta}{IG}$, so $G = \frac{\theta/I}{\theta/V}$. Current sensitivity $= 5$ div/mA $= 5000$ div/A. $G = \frac{5000}{20} = 250\ \Omega$. Answer: (1).
30	Work, Energy and PowerMotion in a vertical circle	Class 11: Work, Energy and Power	Single correctEasy
A easy single correct question on motion in a vertical circle, from Work, Energy and Power. NCERT: Class 11: Work, Energy and Power To just complete a vertical circle of radius R, the speed at the bottom A must be $v = \sqrt{5gR}$. Energy conservation from rest at height h down to A: $mgh = \frac{1}{2}mv^2 = \frac{5}{2}mgR$, so $h = \frac{5}{2}R$. With $R = \frac{D}{2}$: $h = \frac{5}{4}D$. Answer: (4).
31	Motion of System of Particles and Rigid BodyMoment of inertia	Class 11: Systems of Particles and Rotational Motion	Single correctEasy
A easy single correct question on moment of inertia, from Motion of System of Particles and Rigid Body. NCERT: Class 11: Systems of Particles and Rotational Motion The work needed to stop each body equals its rotational kinetic energy $\frac{1}{2}I\omega^2$, so with the same $\omega$, $W \propto I$. Solid sphere $I_A = \frac{2}{5}MR^2$; disk $I_B = \frac{1}{2}MR^2$; ring $I_C = MR^2$. $I_C > I_B > I_A$, so $W_C > W_B > W_A$. Answer: (3).
32	Work, Energy and PowerCollisions	Class 11: Work, Energy and Power	Single correctEasy
A easy single correct question on collisions, from Work, Energy and Power. NCERT: Class 11: Work, Energy and Power Momentum: $mv + 0 = 0 + 4mv' \Rightarrow v' = \frac{v}{4}$. $e = \frac{\text{speed of separation}}{\text{speed of approach}} = \frac{v' - 0}{v - 0} = \frac{1}{4} = 0.25$. Answer: (2).
33	Laws of MotionFriction	Class 11: Laws of Motion	Single correctEasy
A easy single correct question on friction, from Laws of Motion. NCERT: Class 11: Laws of Motion (1) True: friction opposes relative motion (or its tendency) between surfaces in contact. (2) True: $f_{s,max} = \mu_sN$. (3) True: rolling friction is much smaller than sliding friction. (4) False: $\mu = \frac{f}{N}$ is a ratio of two forces, so it is dimensionless. Answer: (4).
34	KinematicsMotion in a straight line	Class 11: Motion in a Straight Line; Class 11: Motion in a Plane	Single correctMedium
A medium single correct question on motion in a straight line, from Kinematics. NCERT: Class 11: Motion in a Straight Line; Class 11: Motion in a Plane Acceleration $a = \frac{6}{1} = 6$ m/s$^2$ for the first second; after the reversal it is $-6$ m/s$^2$. 0–1 s: displacement $\frac{1}{2}\times6\times1^2 = 3$ m; velocity at 1 s is 6 m/s. 1–2 s: velocity falls from 6 to 0; displacement $6\times1 - \frac{1}{2}\times6\times1^2 = 3$ m. 2–3 s: the car moves back from rest; displacement $-\frac{1}{2}\times6\times1^2 = -3$ m (distance 3 m). Net displacement $= 3 + 3 - 3 = 3$ m; distance $= 3 + 3 + 3 = 9$ m. Average velocity $= \frac{3}{3} = 1$ m/s; average speed $= \frac{9}{3} = 3$ m/s. Answer: (2).
35	Laws of MotionNewton's laws	Class 11: Laws of Motion	Single correctMedium
A medium single correct question on newton's laws, from Laws of Motion. NCERT: Class 11: Laws of Motion In the frame of the wedge, the block feels a pseudo force $ma$ towards the left, besides its weight mg and the normal reaction (no friction). The incline rises towards the left (vertex A over C), so the pseudo force has a component $ma\cos\theta$ up the incline, while gravity has a component $mg\sin\theta$ down the incline. For the block to stay at rest relative to the wedge: $ma\cos\theta = mg\sin\theta \Rightarrow a = g\tan\theta$. Answer: (4).
36	Motion of System of Particles and Rigid BodyTorque and rotational dynamics	Class 11: Systems of Particles and Rotational Motion	Single correctEasy
A easy single correct question on torque and rotational dynamics, from Motion of System of Particles and Rigid Body. NCERT: Class 11: Systems of Particles and Rotational Motion Position of the point of application relative to (2, –2, –2): $\vec{r} = (2-2)\hat{i} + (0+2)\hat{j} + (-3+2)\hat{k} = 2\hat{j} - \hat{k}$. $\vec{\tau} = \vec{r}\times\vec{F} = \begin{vmatrix}\hat{i}&\hat{j}&\hat{k}\\0&2&-1\\4&5&-6\end{vmatrix}$ $= \hat{i}(2(-6) - (-1)(5)) - \hat{j}(0(-6) - (-1)(4)) + \hat{k}(0\cdot5 - 2\cdot4)$ $= -7\hat{i} - 4\hat{j} - 8\hat{k}$. Answer: (4).
37	Experimental SkillsVernier calipers and screw gauge	No matching NCERT chapter	Single correctEasy
A easy single correct question on vernier calipers and screw gauge, from Experimental Skills. NCERT: No matching NCERT chapter Observed reading = main scale reading + (circular scale division × least count) $= 0.5$ cm $+ 25\times0.001$ cm $= 0.525$ cm. Correct reading = observed reading – zero error $= 0.525 - (-0.004) = 0.529$ cm. Answer: (4).
38	Motion of System of Particles and Rigid BodyAngular momentum	Class 11: Systems of Particles and Rotational Motion	Single correctEasy
A easy single correct question on angular momentum, from Motion of System of Particles and Rigid Body. NCERT: Class 11: Systems of Particles and Rotational Motion In free space no external torque acts on the sphere, so its angular momentum $L = I\omega$ is conserved. Increasing the radius increases $I = \frac{2}{5}MR^2$, so $\omega$ falls, and the kinetic energy $\frac{L^2}{2I}$ falls too. Only the angular momentum stays the same. Answer: (4).
39	GravitationKepler's laws	Class 11: Gravitation	Single correctEasy
A easy single correct question on kepler's laws, from Gravitation. NCERT: Class 11: Gravitation By conservation of angular momentum (Kepler's second law), the planet moves fastest where it is closest to the Sun. From the figure, the Sun S lies near the end A of the major axis: A is the nearest point (perihelion), C the farthest (aphelion), and B is at an intermediate distance. So $v_A > v_B > v_C$ and $K_A > K_B > K_C$. Answer: (2).
40	GravitationAcceleration due to gravity	Class 11: Gravitation	Single correctMedium
A medium single correct question on acceleration due to gravity, from Gravitation. NCERT: Class 11: Gravitation The acceleration due to gravity on the Earth is $g = \frac{GM_E}{R_E^2}$; it depends on the Earth's mass, not the Sun's. Making G ten times larger makes g ten times larger, whatever happens to the Sun's mass. (1) $T = 2\pi\sqrt{\frac{l}{g}}$ decreases: correct. (2) Our weight increases ten-fold, so walking becomes more difficult: correct. (3) Raindrops are pulled down harder (and their terminal speed grows with g): correct. (4) 'g on the Earth will not change' is not correct. Answer: (4).
41	Motion of System of Particles and Rigid BodyMoment of inertia	Class 11: Systems of Particles and Rotational Motion	Single correctEasy
A easy single correct question on moment of inertia, from Motion of System of Particles and Rigid Body. NCERT: Class 11: Systems of Particles and Rotational Motion For rolling without slipping, $v = \omega R$. $K_t = \frac{1}{2}Mv^2$; $K_r = \frac{1}{2}I\omega^2 = \frac{1}{2}\cdot\frac{2}{5}MR^2\cdot\frac{v^2}{R^2} = \frac{1}{5}Mv^2$. $K_t + K_r = \frac{1}{2}Mv^2 + \frac{1}{5}Mv^2 = \frac{7}{10}Mv^2$. $K_t : (K_t + K_r) = \frac{1}{2} : \frac{7}{10} = 5 : 7$. Answer: (2).
42	Properties of Bulk MatterViscosity	Class 11: Mechanical Properties of Solids; Class 11: Mechanical Properties of Fluids; Class 11: Thermal Properties of Matter	Single correctMedium
A medium single correct question on viscosity, from Properties of Bulk Matter. NCERT: Class 11: Mechanical Properties of Solids; Class 11: Mechanical Properties of Fluids; Class 11: Thermal Properties of Matter Terminal velocity: $v_t = \frac{2r^2(\rho - \sigma)g}{9\eta} \propto r^2$. Viscous force at terminal velocity: $F = 6\pi\eta rv_t$. Rate of heat production = power against the viscous force $= Fv_t = 6\pi\eta rv_t^2 \propto r\cdot(r^2)^2 = r^5$. Answer: (1).
43	Properties of Bulk MatterHeat transfer	Class 11: Mechanical Properties of Solids; Class 11: Mechanical Properties of Fluids; Class 11: Thermal Properties of Matter	Single correctEasy
A easy single correct question on heat transfer, from Properties of Bulk Matter. NCERT: Class 11: Mechanical Properties of Solids; Class 11: Mechanical Properties of Fluids; Class 11: Thermal Properties of Matter Wien's law: $\lambda_mT = $ constant, so $\frac{T'}{T} = \frac{\lambda_0}{\frac{3}{4}\lambda_0} = \frac{4}{3}$. Stefan's law: $P \propto T^4$, so $n = \left(\frac{4}{3}\right)^4 = \frac{256}{81}$. Answer: (1).
44	Properties of Bulk MatterElasticity	Class 11: Mechanical Properties of Solids; Class 11: Mechanical Properties of Fluids; Class 11: Thermal Properties of Matter	Single correctMedium
A medium single correct question on elasticity, from Properties of Bulk Matter. NCERT: Class 11: Mechanical Properties of Solids; Class 11: Mechanical Properties of Fluids; Class 11: Thermal Properties of Matter Same volume: $AL_1 = 3AL_2 \Rightarrow L_2 = \frac{L_1}{3}$. Young's modulus: $\Delta l = \frac{FL}{AY}$, so $F = \frac{AY\Delta l}{L}$. $\frac{F_2}{F_1} = \frac{A_2}{A_1}\cdot\frac{L_1}{L_2} = 3\times3 = 9$. $F_2 = 9F$. Answer: (3).
45	ThermodynamicsFirst law	Class 11: Thermodynamics	Single correctMedium
A medium single correct question on first law, from Thermodynamics. NCERT: Class 11: Thermodynamics Heat supplied: $Q = 54$ cal $= 54\times4.18 = 225.7$ J. Work done by the sample in expanding against the atmosphere: the 0·1 g of water occupies 0·1 cc, so $W = P\Delta V = 1.013\times10^5\times(167.1 - 0.1)\times10^{-6} = 16.9$ J. First law: $\Delta U = Q - W = 225.7 - 16.9 = 208.8$ J $\approx 208.7$ J. Answer: (2).

Chemistry questions, each with its chapter and our explanation
Q	Chapter and topic	NCERT	Kind and level
46	Redox ReactionsOxidation number	Class 11: Redox Reactions	Single correctEasy
A easy single correct question on oxidation number, from Redox Reactions. NCERT: Class 11: Redox Reactions Oxidation state of N in each: $HNO_3$: $+1 + x - 6 = 0 \Rightarrow x = +5$. NO: $x - 2 = 0 \Rightarrow x = +2$. $N_2$: 0 (element). $NH_4Cl$: in $NH_4^+$, $x + 4 = +1 \Rightarrow x = -3$. Decreasing order: $HNO_3$ (+5) > NO (+2) > $N_2$ (0) > $NH_4Cl$ (–3). Answer: (3).
47	p-Block ElementsGroup 13 elements	No matching NCERT chapter	Single correctEasy
A easy single correct question on group 13 elements, from p-Block Elements. NCERT: No matching NCERT chapter Forming $MF_6^{3-}$ needs six electron pairs around M, i.e. a covalency of 6, which needs d orbitals beyond the s and p set. Boron, in the second period, has only 2s and 2p orbitals (no 2d), so its maximum covalency is 4 (as in $BF_4^-$). Al, Ga and In have vacant d orbitals and form $AlF_6^{3-}$, $GaF_6^{3-}$, $InF_6^{3-}$. Answer: (1).
48	Isolation of MetalsSmelting and refining	No matching NCERT chapter	Single correctEasy
A easy single correct question on smelting and refining, from Isolation of Metals. NCERT: No matching NCERT chapter A metal can reduce a metal oxide when its own oxide-formation line lies below that of the oxide in the Ellingham diagram (more negative $\Delta_fG^\circ$), so that the overall $\Delta G^\circ$ of the reduction is negative. The MgO line lies below the $Al_2O_3$ line (at temperatures below about 1350°C to 1500°C), so Mg can reduce alumina. The lines for ZnO, FeO and $Cu_2O$ lie far above that of $Al_2O_3$, so Zn, Fe and Cu cannot. Answer: (1).
49	p-Block ElementsGroup 13 elements	No matching NCERT chapter	Single correctMedium
A medium single correct question on group 13 elements, from p-Block Elements. NCERT: No matching NCERT chapter Atomic radius generally increases down the group, but Ga (135 pm) is slightly smaller than Al (143 pm): the ten 3d electrons in Ga shield the nucleus poorly, so the extra nuclear charge pulls the outer electrons in. Radii (pm): B 85, Ga 135, Al 143, In 167, Tl 170. Order: B < Ga < Al < In < Tl. Answer: (4).
50	p-Block ElementsGroup 17 and 18 elements	No matching NCERT chapter	Single correctMedium
A medium single correct question on group 17 and 18 elements, from p-Block Elements. NCERT: No matching NCERT chapter (1) True: fluorine, the most electronegative element, shows only the –1 state; Cl, Br and I also show +1, +3, +5, +7. (2) True: all halogens are oxidising agents ($F_2$ the strongest, $I_2$ the weakest). (3) Not true: fluorine, being the most electronegative element, does not form the series of oxoacids the others form (only the unstable HOF is known), and of the others iodine also forms periodic acid $H_5IO_6$, which is not monobasic. The general statement that all halogens form monobasic oxyacids fails. (4) True: chlorine has the most negative electron-gain enthalpy of all elements (–349 kJ/mol); fluorine's is less negative because of electron–electron repulsion in its small 2p shell. Answer: (3).
51	Chemical Bonding and Molecular StructureVSEPR theory	Class 11: Chemical Bonding and Molecular Structure	Single correctEasy
A easy single correct question on vsepr theory, from Chemical Bonding and Molecular Structure. NCERT: Class 11: Chemical Bonding and Molecular Structure Cl has 7 valence electrons; three of them form bonds with the three F atoms. The remaining 4 electrons make 2 lone pairs. With 3 bond pairs + 2 lone pairs (sp³d), the molecule is T-shaped. Answer: (2).
52	Alcohols, Phenols and EthersPreparation and properties	Class 12: Alcohols, Phenols and Ethers	Single correctMedium
A medium single correct question on preparation and properties, from Alcohols, Phenols and Ethers. NCERT: Class 12: Alcohols, Phenols and Ethers Step 1 (Friedel–Crafts alkylation): with anhydrous $AlCl_3$, $CH_3CH_2CH_2Cl$ gives the primary carbocation $CH_3CH_2CH_2^+$, which rearranges by a hydride shift to the more stable secondary carbocation $(CH_3)_2CH^+$. Benzene is alkylated by it, so P is cumene (isopropylbenzene), $C_6H_5CH(CH_3)_2$. Step 2 (cumene process): $O_2$ converts cumene into cumene hydroperoxide $C_6H_5C(CH_3)_2OOH$, which with dilute acid rearranges and splits into phenol and acetone. Q = phenol, $C_6H_5OH$; R = acetone, $CH_3COCH_3$. Answer: (4).
53	BiomoleculesProteins	Class 12: Biomolecules	Single correctEasy
A easy single correct question on proteins, from Biomolecules. NCERT: Class 12: Biomolecules A zwitterion carries both a positive and a negative charge in one molecule; it forms when a molecule has both an acidic and a basic group, so that the acid protonates the base internally. Glycine, $H_2N-CH_2-COOH$, has both an amino group and a carboxyl group, and exists as $H_3N^+-CH_2-COO^-$. Benzoic acid has only an acidic group, aniline only a basic group, and in acetanilide the N is an amide nitrogen and there is no acidic group. Answer: (4).
54	PolymersNylon, Teflon, Bakelite and PVC	No matching NCERT chapter	Single correctMedium
A medium single correct question on nylon, teflon, bakelite and pvc, from Polymers. NCERT: No matching NCERT chapter Cross-linked (network) polymers are usually formed from bi-functional and tri-functional monomers and contain strong covalent bonds between the various linear polymer chains, e.g. bakelite and melamine. So statements (1), (2) and (3) describe them correctly. Statement (4) misplaces the feature that defines these polymers: what makes a polymer cross-linked is the covalent bonds between the chains (the cross-links), not the bonds within each chain, which every polymer has. As a description of network polymers it is the incorrect one. Answer: (4).
55	AminesBasicity of amines	Class 12: Amines	Single correctEasy
A easy single correct question on basicity of amines, from Amines. NCERT: Class 12: Amines The $-NH_2$ group is ortho/para directing. But in the strongly acidic nitrating mixture, much of the aniline is protonated to the anilinium ion $C_6H_5NH_3^+$. The $-NH_3^+$ group has no lone pair and withdraws electrons, so it is deactivating and meta directing. Hence a good amount (about 47%) of m-nitroaniline is formed along with the p- and o-isomers. Answer: (4).
56	BiomoleculesCarbohydrates	Class 12: Biomolecules	Single correctEasy
A easy single correct question on carbohydrates, from Biomolecules. NCERT: Class 12: Biomolecules Amylose is a long unbranched chain of α-D-glucose units joined by C1→C4 α-glycosidic links. Amylopectin is branched: its chains are joined by C1→C4 α-links, and the branches by C1→C6 α-links. Neither has β-links, and both contain only glucose. So the difference is that amylopectin has both 1→4 α and 1→6 α linkages. Answer: (3).
57	Some Basic Concepts of ChemistryStoichiometry	Class 11: Some Basic Concepts of Chemistry	Single correctMedium
A medium single correct question on stoichiometry, from Some Basic Concepts of Chemistry. NCERT: Class 11: Some Basic Concepts of Chemistry Concentrated $H_2SO_4$ dehydrates both acids: $HCOOH \rightarrow CO + H_2O$; $\frac{2.3}{46} = 0.05$ mol HCOOH gives 0.05 mol CO. $H_2C_2O_4 \rightarrow CO + CO_2 + H_2O$; $\frac{4.5}{90} = 0.05$ mol oxalic acid gives 0.05 mol CO and 0.05 mol $CO_2$. KOH pellets absorb the $CO_2$ (and the water); CO, a neutral oxide, passes through. Remaining: $0.05 + 0.05 = 0.1$ mol CO $= 0.1\times28 = 2.8$ g. Answer: (1).
58	Classification of Elements and PeriodicityPeriodic trends	Class 11: Classification of Elements and Periodicity in Properties	Single correctEasy
A easy single correct question on periodic trends, from Classification of Elements and Periodicity. NCERT: Class 11: Classification of Elements and Periodicity in Properties Down group 2 the metallic character rises, so the oxides become more basic: BeO < MgO < CaO < BaO in basic strength. BeO is amphoteric (it dissolves in both acids and alkalis), while the others are basic. So BeO is the most acidic of the four. Answer: (2).
59	Environmental ChemistryAir and water pollution	No matching NCERT chapter	Single correctEasy
A easy single correct question on air and water pollution, from Environmental Chemistry. NCERT: No matching NCERT chapter NO and $NO_2$ are formed in lightning and in high-temperature combustion (engines, power plants), and $N_2O$ comes from soil bacteria and from fertilisers; all three are common atmospheric pollutants with both natural and human sources. $N_2O_5$ is an unstable solid anhydride that is not released into the air in any significant amount from either source. Answer: (3).
60	Alcohols, Phenols and EthersWilliamson synthesis	Class 12: Alcohols, Phenols and Ethers	Single correctEasy
A easy single correct question on williamson synthesis, from Alcohols, Phenols and Ethers. NCERT: Class 12: Alcohols, Phenols and Ethers A = ethanol. $2C_2H_5OH + 2Na \rightarrow 2C_2H_5ONa + H_2$: B = sodium ethoxide. $C_2H_5OH + PCl_5 \rightarrow C_2H_5Cl + POCl_3 + HCl$: C = chloroethane. Williamson synthesis: $C_2H_5ONa + C_2H_5Cl \rightarrow C_2H_5OC_2H_5 + NaCl$ (diethyl ether). Order: $C_2H_5OH$, $C_2H_5ONa$, $C_2H_5Cl$. Answer: (4).
61	HydrocarbonsElectrophilic substitution and directive influence	Class 11: Hydrocarbons	Single correctMedium
A medium single correct question on electrophilic substitution and directive influence, from Hydrocarbons. NCERT: Class 11: Hydrocarbons $C_7H_8$ is toluene, $C_6H_5CH_3$. $3Cl_2$ with heat (no catalyst) chlorinates the side chain by free radicals: A = benzotrichloride, $C_6H_5CCl_3$. $Br_2/Fe$ brominates the ring. The $-CCl_3$ group is strongly electron-withdrawing and meta directing: B = m-bromobenzotrichloride, $m-BrC_6H_4CCl_3$. Zn/HCl reduces $-CCl_3$ back to $-CH_3$: C = m-bromotoluene. Answer: (3).
62	HydrocarbonsAlkanes	Class 11: Hydrocarbons	Single correctEasy
A easy single correct question on alkanes, from Hydrocarbons. NCERT: Class 11: Hydrocarbons Ethene and ethyne react with bromine by addition, not substitution, so A is an alkane. Wurtz reaction doubles the carbon chain: $2RBr + 2Na \rightarrow R-R + 2NaBr$. From $CH_4$: $CH_3Br \rightarrow CH_3-CH_3$ (2 carbon atoms, fewer than four). From $CH_3CH_3$: $C_2H_5Br \rightarrow C_4H_{10}$ (four carbon atoms, not fewer than four). So A is methane. Answer: (4).
63	Chemical Bonding and Molecular StructureHybridisation	Class 11: Chemical Bonding and Molecular Structure	Single correctEasy
A easy single correct question on hybridisation, from Chemical Bonding and Molecular Structure. NCERT: Class 11: Chemical Bonding and Molecular Structure A carbon in a double bond (and no triple bond) is $sp^2$; a carbon in a triple bond is sp; a carbon with only single bonds is $sp^3$. (1) $sp^2, sp^2, sp^2, sp^2$. (2) $CH_2=CH-C\equiv CH$: $sp^2, sp^2, sp, sp$. (3) $sp, sp, sp, sp$. (4) $sp^3, sp^2, sp^2, sp^3$. Answer: (2).
64	HydrocarbonsElectrophilic substitution and directive influence	Class 11: Hydrocarbons	Single correctMedium
A medium single correct question on electrophilic substitution and directive influence, from Hydrocarbons. NCERT: Class 11: Hydrocarbons Each is the arenium ion (σ-complex) formed when an electrophile Y attacks nitrobenzene; the $sp^3$ carbon carries H and Y. In such an ion the positive charge is spread over the carbons ortho and para to the $sp^3$ carbon. (2) Attack para to $NO_2$: the + charge sits on the carbon bearing $NO_2$, as drawn. (4) Attack ortho to $NO_2$: again the + charge is drawn on the carbon bearing $NO_2$. (3) Attack para to $NO_2$ (the $sp^3$ carbon is opposite the $NO_2$ carbon), so one resonance form puts + on the carbon bearing $NO_2$. (1) Attack meta to $NO_2$: the + charge is spread over the carbons ortho and para to the $sp^3$ carbon, and never reaches the carbon bearing $NO_2$. A positive charge next to the strongly electron-withdrawing $NO_2$ group is badly destabilised, so the ion in which the charge never sits on that carbon, (1), is the most stable. (This is why $NO_2$ is meta directing.) Answer: (1).
65	Organic Chemistry: Some Basic Principles and TechniquesElectronic effects	Class 11: Organic Chemistry – Some Basic Principles and Techniques	Single correctEasy
A easy single correct question on electronic effects, from Organic Chemistry: Some Basic Principles and Techniques. NCERT: Class 11: Organic Chemistry – Some Basic Principles and Techniques The –I (electron-withdrawing inductive) effect grows with the electronegativity of the atom attached to carbon: F (4.0) > O (3.5) > N (3.0). So $-F > -OR > -NR_2$ (and likewise $> -NH_2$); the alkyl groups on N, being electron-releasing, make $-NR_2$ even less withdrawing than $-NH_2$. Written in increasing order: $-NR_2 < -OR < -F$. Answer: (2).
66	Alcohols, Phenols and EthersReactions of phenols	Class 12: Alcohols, Phenols and Ethers	Single correctEasy
A easy single correct question on reactions of phenols, from Alcohols, Phenols and Ethers. NCERT: Class 12: Alcohols, Phenols and Ethers This is the Reimer–Tiemann reaction. The base removes a proton from chloroform, and the trichloromethyl anion loses $Cl^-$: $CHCl_3 + OH^- \rightarrow {}^-CCl_3 + H_2O$; ${}^-CCl_3 \rightarrow :CCl_2 + Cl^-$. Dichlorocarbene, an electron-deficient species, is the electrophile; it attacks the ortho position of the phenoxide ion, and the $-CHCl_2$ group formed is hydrolysed to $-CHO$, giving the salt of salicylaldehyde. Answer: (4).
67	Chemical Bonding and Molecular StructureHydrogen bonding	Class 11: Chemical Bonding and Molecular Structure	Single correctEasy
A easy single correct question on hydrogen bonding, from Chemical Bonding and Molecular Structure. NCERT: Class 11: Chemical Bonding and Molecular Structure Carboxylic acid molecules are held together by strong intermolecular hydrogen bonds; each C=O and O–H pair links two molecules into a cyclic dimer that persists even in the vapour. Breaking these needs more energy than the weaker H-bonds of alcohols or the dipole attractions of aldehydes and ketones, so the boiling points are higher. Answer: (4).
68	Aldehydes, Ketones and Carboxylic AcidsTests to distinguish aldehydes and ketones	Class 12: Aldehydes, Ketones and Carboxylic Acids	Single correctMedium
A medium single correct question on tests to distinguish aldehydes and ketones, from Aldehydes, Ketones and Carboxylic Acids. NCERT: Class 12: Aldehydes, Ketones and Carboxylic Acids The yellow precipitate with a characteristic smell is iodoform, $CHI_3$. NaOI is made from iodine and NaOH ($I_2 + 2NaOH \rightarrow NaOI + NaI + H_2O$), so Y is $I_2$. The iodoform test is given by compounds with a $CH_3CO-$ group or a $CH_3CH(OH)-$ group (which NaOI first oxidises to $CH_3CO-$). (1) 1-phenylethanol, $C_6H_5CH(OH)CH_3$ ($C_8H_{10}O$), has the $CH_3CH(OH)-$ group: it gives iodoform. (2) 2-phenylethanol, (3) 4-methylbenzyl alcohol and (4) the dimethylphenol have no such group and do not. Answer: (1).
69	d- and f-Block ElementsTransition element properties	Class 12: The d- and f-Block Elements	MatchingMedium
A medium matching question on transition element properties, from d- and f-Block Elements. NCERT: Class 12: The d- and f-Block Elements Spin-only moment $\mu = \sqrt{n(n+2)}$ B.M., with n unpaired electrons (free ions, so high spin). a. $Co^{3+}$: $3d^6$, n = 4, $\mu = \sqrt{24}$ → iv. b. $Cr^{3+}$: $3d^3$, n = 3, $\mu = \sqrt{15}$ → v. c. $Fe^{3+}$: $3d^5$, n = 5, $\mu = \sqrt{35}$ → ii. d. $Ni^{2+}$: $3d^8$, n = 2, $\mu = \sqrt{8}$ → i. a-iv, b-v, c-ii, d-i. Answer: (3).
70	d- and f-Block ElementsPotassium dichromate and permanganate	Class 12: The d- and f-Block Elements	Single correctMedium
A medium single correct question on potassium dichromate and permanganate, from d- and f-Block Elements. NCERT: Class 12: The d- and f-Block Elements d-d transitions and paramagnetism both need unpaired d electrons. $MnO_4^-$: Mn(+7), $3d^0$. $Cr_2O_7^{2-}$ and $CrO_4^{2-}$: Cr(+6), $3d^0$. These have no d electrons; they are diamagnetic, and their colour comes from charge transfer, not d-d transitions. $MnO_4^{2-}$: Mn(+6), $3d^1$, one unpaired electron: paramagnetic, and a d-d transition is possible. Answer: (4).
71	Coordination CompoundsValence bond theory	Class 12: Coordination Compounds	Single correctEasy
A easy single correct question on valence bond theory, from Coordination Compounds. NCERT: Class 12: Coordination Compounds $Fe(CO)_5$ contains a single iron atom bonded to five CO ligands (trigonal bipyramidal), so it is a mononuclear carbonyl. (Dinuclear and trinuclear iron carbonyls are $Fe_2(CO)_9$ and $Fe_3(CO)_{12}$.) Answer: (2).
72	Coordination CompoundsIsomerism in complexes	Class 12: Coordination Compounds	Single correctEasy
A easy single correct question on isomerism in complexes, from Coordination Compounds. NCERT: Class 12: Coordination Compounds $[CoCl_2(en)_2]$ is an octahedral complex of type $[M(AA)_2B_2]$: the two Cl ligands can be adjacent (cis) or opposite (trans), so it shows geometrical isomerism (the cis form is also optically active). There is no counter-ion to exchange (ionization), only one metal centre (coordination), and no ambidentate ligand (linkage). Answer: (3).
73	Coordination CompoundsValence bond theory	Class 12: Coordination Compounds	Single correctEasy
A easy single correct question on valence bond theory, from Coordination Compounds. NCERT: Class 12: Coordination Compounds In $[Ni(CO)_4]$, nickel is in the 0 state: $3d^84s^2$. The strong-field CO ligands pair the electrons into $3d^{10}$, leaving 4s and 4p empty for $sp^3$ hybridisation. $sp^3$ → tetrahedral; no unpaired electrons → diamagnetic. Answer: (2).
74	EquilibriumpH and buffers	Class 11: Equilibrium	Single correctMedium
A medium single correct question on ph and buffers, from Equilibrium. NCERT: Class 11: Equilibrium pH 1 needs $[H^+] = 0.1$ M after neutralisation. a. HCl 6 mmol – NaOH 4 mmol = 2 mmol $H^+$ in 100 mL → 0.02 M (pH 1.7). b. 5.5 – 4.5 = 1 mmol in 100 mL → 0.01 M (pH 2). c. HCl $75\times0.2 = 15$ mmol – NaOH $25\times0.2 = 5$ mmol = 10 mmol in 100 mL → 0.1 M (pH 1). d. 10 – 10 = 0: neutral (pH 7). Solution c has pH 1. Answer: (4).
75	Surface ChemistryColloids and their preparation	No matching NCERT chapter	Single correctEasy
A easy single correct question on colloids and their preparation, from Surface Chemistry. NCERT: No matching NCERT chapter By the Hardy–Schulze rule, a colloid is coagulated by the ions carrying charge opposite to that of the colloidal particles (so the sign matters), and the coagulating power rises steeply with the magnitude of that charge (e.g. $Al^{3+} > Ba^{2+} > Na^+$ for a negative sol). Answer: (1).
76	States of MatterGas laws	No matching NCERT chapter	Single correctEasy
A easy single correct question on gas laws, from States of Matter. NCERT: No matching NCERT chapter The van der Waals constant a measures the intermolecular attraction (the values given are values of a). The larger a is, the stronger the attraction and the more easily the gas liquefies. $NH_3$ has the largest a (4·17), so it is the most easily liquefied. Answer: (3).
77	EquilibriumSolubility product	Class 11: Equilibrium	Single correctEasy
A easy single correct question on solubility product, from Equilibrium. NCERT: Class 11: Equilibrium Molar solubility $s = \frac{2.42\times10^{-3}}{233} = 1.04\times10^{-5}$ mol/L. $BaSO_4 \rightleftharpoons Ba^{2+} + SO_4^{2-}$, so $K_{sp} = s^2 = (1.04\times10^{-5})^2 = 1.08\times10^{-10}$ mol$^2$ L$^{-2}$. Answer: (3).
78	Some Basic Concepts of ChemistryMole concept	Class 11: Some Basic Concepts of Chemistry	Single correctEasy
A easy single correct question on mole concept, from Some Basic Concepts of Chemistry. NCERT: Class 11: Some Basic Concepts of Chemistry Compare moles: (1) $\frac{0.00224}{22.4} = 10^{-4}$ mol. (2) $\frac{0.18}{18} = 10^{-2}$ mol. (3) 18 mL of liquid water (density 1 g/mL) = 18 g = 1 mol. (4) $10^{-3}$ mol. 18 mL of water has the most molecules ($6.022\times10^{23}$). Answer: (3).
79	Chemical KineticsIntegrated rate laws and half-life	Class 12: Chemical Kinetics	Single correctEasy
A easy single correct question on integrated rate laws and half-life, from Chemical Kinetics. NCERT: Class 12: Chemical Kinetics First order: $t_{1/2} = \frac{0.693}{k}$, independent of $[A]_0$. Second order: $t_{1/2} = \frac{1}{k[A]_0}$, which depends on $[A]_0$. So (2) is correct. (1) is wrong: reactions of any order can be catalysed. (3) and (4) are wrong: the rates of both depend on concentration (rate = k[A] and rate = $k[A]^2$). Answer: (2).
80	HydrogenHydrogen and its compounds	No matching NCERT chapter	Single correctEasy
A easy single correct question on hydrogen and its compounds, from Hydrogen. NCERT: No matching NCERT chapter Going down group 2 the metal becomes larger and more electropositive, so the hydrides become more ionic. $BeH_2$, with the small, highly polarising $Be^{2+}$, is covalent (polymeric). Order of ionic character: $BeH_2 < CaH_2 < BaH_2$. Answer: (3).
81	ElectrochemistryElectrochemical cells	Class 12: Electrochemistry	Single correctMedium
A medium single correct question on electrochemical cells, from Electrochemistry. NCERT: Class 12: Electrochemistry A species disproportionates when the potential for its reduction (couple to its right) is higher than the potential for its formation from the species on its left, so that $E^\circ_{cell} = E^\circ_{right} - E^\circ_{left} > 0$. Diagram: $BrO_4^- \xrightarrow{1.82} BrO_3^- \xrightarrow{1.5} HBrO \xrightarrow{1.595} Br_2 \xrightarrow{1.0652} Br^-$. $BrO_3^-$: $1.5 - 1.82 < 0$, no. HBrO: $1.595 - 1.5 = +0.095$ V > 0, so $\Delta G^\circ < 0$: HBrO disproportionates into $BrO_3^-$ and $Br_2$. $Br_2$: $1.0652 - 1.595 < 0$, no. $BrO_4^-$ is the highest state and cannot disproportionate. Answer: (4).
82	Redox ReactionsBalancing redox equations	Class 11: Redox Reactions	Single correctEasy
A easy single correct question on balancing redox equations, from Redox Reactions. NCERT: Class 11: Redox Reactions Reduction: $MnO_4^- + 8H^+ + 5e^- \rightarrow Mn^{2+} + 4H_2O$ (Mn +7 → +2). Oxidation: $C_2O_4^{2-} \rightarrow 2CO_2 + 2e^-$ (C +3 → +4). Multiply by 2 and 5 to match electrons (10): $2MnO_4^- + 5C_2O_4^{2-} + 16H^+ \rightarrow 2Mn^{2+} + 10CO_2 + 8H_2O$. Coefficients: $MnO_4^-$ 2, $C_2O_4^{2-}$ 5, $H^+$ 16. Answer: (2).
83	EquilibriumLe Chatelier's principle	Class 11: Equilibrium	Single correctEasy
A easy single correct question on le chatelier's principle, from Equilibrium. NCERT: Class 11: Equilibrium The forward reaction is exothermic ($\Delta_rH < 0$), so by Le Chatelier's principle a low temperature favours the product. Two moles of gas give one mole ($\Delta n_g = -1$), so a high pressure favours the product. Answer: (3).
84	Chemical KineticsIntegrated rate laws and half-life	Class 12: Chemical Kinetics	Single correctEasy
A easy single correct question on integrated rate laws and half-life, from Chemical Kinetics. NCERT: Class 12: Chemical Kinetics For a zero order reaction, $[A] = [A]_0 - kt$, so $t_{1/2} = \frac{[A]_0}{2k} \propto [A]_0$. Doubling $[A]_0$ doubles the half-life. Answer: (2).
85	ThermodynamicsEnthalpy	Class 11: Thermodynamics	Single correctMedium
A medium single correct question on enthalpy, from Thermodynamics. NCERT: Class 11: Thermodynamics Let the bond energies be $X_2 = a$, $Y_2 = 0.5a$, $XY = a$. Formation of XY: $\frac{1}{2}X_2 + \frac{1}{2}Y_2 \rightarrow XY$. $\Delta H = \sum(\text{bonds broken}) - \sum(\text{bonds formed}) = \frac{1}{2}a + \frac{1}{2}(0.5a) - a = -0.25a$. $-0.25a = -200 \Rightarrow a = 800$ kJ/mol. Answer: (1).
86	States of MatterGas laws	No matching NCERT chapter	Single correctEasy
A easy single correct question on gas laws, from States of Matter. NCERT: No matching NCERT chapter In the van der Waals equation $\left(P + \frac{an^2}{V^2}\right)(V - nb) = nRT$, the term $\frac{an^2}{V^2}$ corrects the pressure for the attraction between molecules (a molecule about to hit the wall is pulled back by the others). The constant b corrects for the volume of the molecules. So 'a' corresponds to the forces of attraction between the gas molecules. Answer: (4).
87	Chemical Bonding and Molecular StructureMolecular orbital theory	Class 11: Chemical Bonding and Molecular Structure	Single correctMedium
A medium single correct question on molecular orbital theory, from Chemical Bonding and Molecular Structure. NCERT: Class 11: Chemical Bonding and Molecular Structure Count the electrons and fill the molecular orbitals (for 14 or fewer electrons, $\pi2p$ lies below $\sigma2p$). $CN^-$: 14 electrons, $\sigma1s^2\sigma^1s^2\sigma2s^2\sigma^2s^2\pi2p^4\sigma2p^2$; bond order $\frac{10-4}{2} = 3$. CN: 13 electrons; bond order $\frac{9-4}{2} = 2.5$. $CN^+$: 12 electrons; bond order $\frac{8-4}{2} = 2$. NO: 15 electrons (one in $\pi^*2p$); bond order $\frac{10-5}{2} = 2.5$. $CN^-$ has the highest bond order. Answer: (2).
88	Chemical Bonding and Molecular StructureIonic bonding and lattice enthalpy	Class 11: Chemical Bonding and Molecular Structure	Single correctEasy
A easy single correct question on ionic bonding and lattice enthalpy, from Chemical Bonding and Molecular Structure. NCERT: Class 11: Chemical Bonding and Molecular Structure X has 7 electrons, $1s^22s^22p^3$: it is nitrogen, which gains 3 electrons to form $X^{3-}$ ($N^{3-}$). Magnesium forms $Mg^{2+}$. Balancing charges: $3\times(+2) + 2\times(-3) = 0$, so the formula is $Mg_3X_2$ (magnesium nitride, $Mg_3N_2$). Answer: (4).
89	Solid StatePacking in fcc, bcc and hcp	No matching NCERT chapter	Single correctMedium
A medium single correct question on packing in fcc, bcc and hcp, from Solid State. NCERT: No matching NCERT chapter $\rho = \frac{ZM}{N_Aa^3}$, so with the same M and r, $\rho \propto \frac{Z}{a^3}$. bcc: Z = 2, $a = \frac{4r}{\sqrt{3}}$, $a^3 = \frac{64r^3}{3\sqrt{3}}$. fcc: Z = 4, $a = 2\sqrt{2}r$, $a^3 = 16\sqrt{2}r^3$. $\frac{\rho_{bcc}}{\rho_{fcc}} = \frac{2\cdot3\sqrt{3}/64}{4/(16\sqrt{2})} = \frac{6\sqrt{3}}{64}\times4\sqrt{2} = \frac{3\sqrt{3}\sqrt{2}}{8} = \frac{3\sqrt{3}}{4\sqrt{2}}$ (since $\frac{\sqrt{2}}{8} = \frac{1}{4\sqrt{2}}$). Numerically about 0·92: iron is less dense in the bcc form. Answer: (1).
90	Structure of AtomElectronic configuration	Class 11: Structure of Atom	Single correctEasy
A easy single correct question on electronic configuration, from Structure of Atom. NCERT: Class 11: Structure of Atom (1) Wrong: the boxes show $1s^2\,2s^2\,2p_x^1\,2p_y^1\,2p_z^1$ with the $2p_z$ electron spin opposite to the other two. By Hund's rule the three unpaired 2p electrons of nitrogen must all have parallel spins. (2) Correct: n, l and $m_l$ fix an orbital; the spin quantum number $m_s$ is needed in addition for an electron. (3) Correct: for an s orbital l = 0, so the orbital angular momentum $\sqrt{l(l+1)}\frac{h}{2\pi} = 0$. (4) Correct: the $d_{z^2}$ orbital corresponds to $m_l = 0$. Answer: (1).

Botany questions, each with its chapter and our explanation
Q	Chapter and topic	NCERT	Kind and level
91	Photosynthesis in Higher PlantsLight reaction	Class 11: Photosynthesis in Higher Plants	Single correctEasy
A easy single correct question on light reaction, from Photosynthesis in Higher Plants. NCERT: Class 11: Photosynthesis in Higher Plants Oxygen is given off only when water is the source of electrons (hydrogen) for photosynthesis: the splitting of water in photosystem II releases O$_2$. This oxygenic photosynthesis is found in all plants (Cycas, a gymnosperm; Chara, a green alga) and in cyanobacteria such as Nostoc. Van Niel's work on purple and green sulphur bacteria showed that these bacteria use hydrogen sulphide, not water, as the hydrogen donor: $2H_2S + CO_2 \rightarrow (CH_2O) + H_2O + 2S$. Sulphur, not oxygen, is the by-product, so their photosynthesis is anoxygenic. Answer: (3) Green sulphur bacteria.
92	Sexual Reproduction in Flowering PlantsDouble fertilisation	Class 12: Sexual Reproduction in Flowering Plants	Single correctEasy
A easy single correct question on double fertilisation, from Sexual Reproduction in Flowering Plants. NCERT: Class 12: Sexual Reproduction in Flowering Plants The pollen tube releases two male gametes into the synergid of the embryo sac. - One male gamete fuses with the egg cell: syngamy, giving the diploid zygote. - The other fuses with the two polar nuclei of the central cell: triple fusion, giving the triploid primary endosperm nucleus. Because two fusions take place in one embryo sac, the event is called double fertilisation. Option (2) describes only triple fusion, and (1) and (3) do not happen. Answer: (4) Syngamy and triple fusion.
93	Sexual Reproduction in Flowering PlantsPollination and outbreeding devices	Class 12: Sexual Reproduction in Flowering Plants	Single correctEasy
A easy single correct question on pollination and outbreeding devices, from Sexual Reproduction in Flowering Plants. NCERT: Class 12: Sexual Reproduction in Flowering Plants In some insect-pollinated plants the floral reward is a safe place to lay eggs. A species of moth and the plant Yucca depend on each other completely: the moth lays its eggs in the locule of the ovary and, while doing so, pollinates the flower; the moth's larvae come out of the eggs as the seeds start developing and feed on some of them. Neither the moth nor Yucca can complete its life cycle without the other. (Hydrilla is water-pollinated, and Viola has cleistogamous flowers.) Answer: (2) Yucca.
94	Sexual Reproduction in Flowering PlantsMicrosporogenesis	Class 12: Sexual Reproduction in Flowering Plants	Single correctEasy
A easy single correct question on microsporogenesis, from Sexual Reproduction in Flowering Plants. NCERT: Class 12: Sexual Reproduction in Flowering Plants Pollen grains of many species can be stored for years in liquid nitrogen at −196 °C (cryopreservation). Such pollen banks are used in crop breeding programmes, much like seed banks. −196 °C is the boiling point of liquid nitrogen at atmospheric pressure. Answer: (1) −196 °C.
95	Mineral NutritionEssential elements and their functions	No matching NCERT chapter	Single correctEasy
A easy single correct question on essential elements and their functions, from Mineral Nutrition. NCERT: No matching NCERT chapter Potassium is absorbed as K$^+$ and is present in large amounts in meristematic tissues, buds, leaves and root tips. It helps to maintain the anion–cation balance in cells, is involved in protein synthesis, in the opening and closing of stomata and in the activation of enzymes, and it is the element that maintains the turgidity of cells. Magnesium is a part of chlorophyll, calcium of the middle lamella, and sodium is not an essential element for most plants. Answer: (1) Potassium.
96	Respiration in PlantsETS and oxidative phosphorylation	Class 11: Respiration in Plants	Single correctEasy
A easy single correct question on ets and oxidative phosphorylation, from Respiration in Plants. NCERT: Class 11: Respiration in Plants NAD$^+$ (nicotinamide adenine dinucleotide) is a coenzyme. In glycolysis and the Krebs cycle the dehydrogenases remove hydrogen atoms (electrons) from the substrates and hand them to NAD$^+$, which is reduced to NADH + H$^+$. NADH carries these electrons to complex I of the electron transport system, where it is oxidised back to NAD$^+$ and the energy released drives ATP synthesis. So NAD$^+$ is an electron (hydrogen) carrier. It is not itself an enzyme (it is a coenzyme), it is not a nucleotide source for ATP, and in anaerobic respiration (fermentation) the final acceptor is an organic molecule such as pyruvic acid or acetaldehyde, which is reduced by NADH. Answer: (2).
97	Mineral NutritionEssential elements and their functions	No matching NCERT chapter	Single correctMedium
A medium single correct question on essential elements and their functions, from Mineral Nutrition. NCERT: No matching NCERT chapter The textbook account of iron as a micronutrient: plants obtain iron in the form of ferric ions (Fe$^{3+}$). It is needed in larger amounts than other micronutrients, is a constituent of ferredoxin and cytochromes, activates catalase, and is essential for chlorophyll formation. Answer: (3) Ferric.
102	Molecular Basis of InheritanceTranscription and translation	Class 12: Molecular Basis of Inheritance	Single correctEasy
A easy single correct question on transcription and translation, from Molecular Basis of Inheritance. NCERT: Class 12: Molecular Basis of Inheritance Check each pair. (1) Wrong. Morgan worked on linkage and recombination in Drosophila; transduction was discovered by Zinder and Lederberg. (2) Wrong. Crossing with the recessive parent is a test cross, and it is done with an F$_1$ (or any individual of unknown genotype), not the F$_2$; a dihybrid cross is a cross involving two characters. (3) Correct. A ribozyme is a nucleic acid (RNA) that acts as an enzyme; in bacteria, the 23S rRNA that catalyses peptide bond formation is a ribozyme. (4) Wrong. Transformation was discovered by Frederick Griffith (1928) in Streptococcus pneumoniae. Answer: (3).
104	Principles of Inheritance and VariationDeviations from Mendelism	Class 12: Principles of Inheritance and Variation	Single correctMedium
A medium single correct question on deviations from mendelism, from Principles of Inheritance and Variation. NCERT: Class 12: Principles of Inheritance and Variation (1) Right. In grasshopper the male has only one X (XO) and the female XX. (2) Right. The I$^A$ and I$^B$ alleles of the ABO system are co-dominant. (3) Wrong. Starch synthesis in pea is controlled by one gene with two alleles (B and b). It is the textbook example of pleiotropy and of how dominance depends on the level at which the phenotype is seen (seed size shows incomplete dominance), not of multiple alleles; the ABO gene, with three alleles, is the example of multiple alleles. (4) Right. Morgan's crosses in Drosophila established linkage; he coined the term. Answer: (3).
105	Principles of Inheritance and VariationMendelian genetics	Class 12: Principles of Inheritance and Variation	Single correctMedium
A medium single correct question on mendelian genetics, from Principles of Inheritance and Variation. NCERT: Class 12: Principles of Inheritance and Variation (1) Wrong. Spliceosomes remove introns from hnRNA (splicing), which is part of processing after transcription, not translation. (2) Correct. The Punnett square, the graphical way of working out the offspring of a cross, was developed by Reginald C. Punnett, a British geneticist. (3) Wrong. The term linkage was coined by T.H. Morgan; Franklin Stahl, with Meselson, proved semiconservative replication. (4) Wrong. Transduction was discovered by Zinder and Lederberg; Sidney Altman is known for discovering the catalytic RNA of ribonuclease P. Answer: (2).
106	Molecular Basis of InheritanceReplication	Class 12: Molecular Basis of Inheritance	Single correctEasy
A easy single correct question on replication, from Molecular Basis of Inheritance. NCERT: Class 12: Molecular Basis of Inheritance Meselson and Stahl (1958) grew Escherichia coli in a medium with $^{15}$NH$_4$Cl as the only nitrogen source for many generations, then moved the cells to a medium with $^{14}$NH$_4$Cl. Separating the DNA by CsCl density-gradient centrifugation, they found hybrid (intermediate) DNA after one generation and equal amounts of hybrid and light DNA after two generations, exactly as semiconservative replication predicts. E. coli is a bacterium. (Taylor later showed the same in Vicia faba chromosomes, but the first proof was in the bacterium.) Answer: (2) Bacterium.
107	Reproduction in OrganismsPhases of life and flowering	No matching NCERT chapter	Single correctEasy
A easy single correct question on phases of life and flowering, from Reproduction in Organisms. NCERT: No matching NCERT chapter Perennial plants usually flower every season once they reach the reproductive phase (mango, jackfruit, papaya, apple). Some plants flower only once in their life: several bamboo species flower once, generally after 50–100 years of vegetative growth, produce a large number of fruits and die. Strobilanthus kunthiana (neelakuranji) flowers once in 12 years. Answer: (3) Bamboo species.
108	Reproduction in OrganismsAsexual and vegetative reproduction	No matching NCERT chapter	Single correctEasy
A easy single correct question on asexual and vegetative reproduction, from Reproduction in Organisms. NCERT: No matching NCERT chapter An offset (as in Pistia and Eichhornia) is a vegetative propagule: a short lateral branch with a rosette of leaves that grows out from the parent and develops into a new plant. Vegetative propagation is a form of asexual reproduction in which the new individual arises from the somatic cells of the parent by mitotic division alone, so the offspring is a clone of the parent. Meiosis takes place only in sexual reproduction, parthenocarpy is fruit formation without fertilisation, and parthenogenesis is development of an embryo from an unfertilised egg. Answer: (2) Mitotic divisions.
109	Molecular Basis of InheritanceLac operon	Class 12: Molecular Basis of Inheritance	Single correctEasy
A easy single correct question on lac operon, from Molecular Basis of Inheritance. NCERT: Class 12: Molecular Basis of Inheritance (1) Wrong. Meselson and Stahl worked on Escherichia coli. (2) Wrong. Hershey and Chase worked on a bacteriophage (T2) infecting E. coli, proving DNA is the genetic material; TMV is the virus in whose case RNA is the genetic material. (3) Wrong. Alec Jeffreys developed DNA fingerprinting using VNTR probes; Streptococcus pneumoniae was Griffith's organism. (4) Correct. Jacob and Monod first elucidated the transcriptionally regulated system, the lac operon of E. coli. Answer: (4).
110	Sexual Reproduction in Flowering PlantsMicrosporogenesis	Class 12: Sexual Reproduction in Flowering Plants	Single correctEasy
A easy single correct question on microsporogenesis, from Sexual Reproduction in Flowering Plants. NCERT: Class 12: Sexual Reproduction in Flowering Plants The hard outer layer of the pollen grain, the exine, is made of sporopollenin, one of the most resistant organic materials known. It withstands high temperatures and strong acids and alkali, and no enzyme that degrades it is known. That is why pollen grains are well preserved as fossils. The intine (cellulose and pectin) is thin and easily destroyed, and pollenkitt is an oily coat that helps insect pollination. Answer: (4) Sporopollenin.
111	Organisms and PopulationsPopulation attributes	Class 12: Organisms and Populations	Single correctEasy
A easy single correct question on population attributes, from Organisms and Populations. NCERT: Class 12: Organisms and Populations Population density changes through four processes: natality (the number of births in a population during a given period), mortality (the number of deaths), immigration (individuals of the same species coming into the habitat) and emigration (individuals leaving it). Natality is thus the birth rate. Answer: (2) Birth rate.
112	Environmental IssuesOzone depletion	No matching NCERT chapter	Single correctEasy
A easy single correct question on ozone depletion, from Environmental Issues. NCERT: No matching NCERT chapter The International Day for the Preservation of the Ozone Layer (World Ozone Day) is observed on 16 September, the day the Montreal Protocol on substances that deplete the ozone layer was signed in 1987. 5 June is World Environment Day and 22 April is Earth Day. Answer: (1) 16th September.
113	Environmental IssuesOzone depletion	No matching NCERT chapter	Single correctEasy
A easy single correct question on ozone depletion, from Environmental Issues. NCERT: No matching NCERT chapter A primary pollutant is emitted directly from its source; a secondary pollutant is formed in the atmosphere by reactions among primary pollutants. SO$_2$, CO$_2$ and CO come straight out of burning fuels, so they are primary. Ground-level ozone (O$_3$) is not emitted: it forms when nitrogen oxides and hydrocarbons from vehicle exhaust react in sunlight (photochemical smog), so it is a secondary pollutant. Answer: (4) O$_3$.
114	Organisms and PopulationsPopulation attributes	Class 12: Organisms and Populations	Single correctEasy
A easy single correct question on population attributes, from Organisms and Populations. NCERT: Class 12: Organisms and Populations The habitat is the physical place where an organism lives; the niche is more than that. Each organism has a range of conditions it can tolerate, resources it uses and a distinct functional role in the ecological system, and all of these together make up its niche. In short, the niche is the functional role played by the organism where it lives. Options (1) and (3) are only parts of the niche, and (2) is the habitat. Answer: (4).
115	EcosystemEcological pyramids	Class 12: Ecosystem	Single correctEasy
A easy single correct question on ecological pyramids, from Ecosystem. NCERT: Class 12: Ecosystem The data are masses (grams), so they make a pyramid of biomass, not of numbers or energy. Drawing the trophic levels with the producers at the base: producers 10 g, primary consumers 60 g, secondary consumers 120 g. The base is the narrowest and the biomass increases at each higher level, so the pyramid is inverted. (Such an inverted pyramid of biomass is seen in the sea, where a small standing crop of phytoplankton supports a large biomass of fish.) Answer: (3) Inverted pyramid of biomass.
116	Environmental IssuesOzone depletion	No matching NCERT chapter	Single correctEasy
A easy single correct question on ozone depletion, from Environmental Issues. NCERT: No matching NCERT chapter Chlorofluorocarbons (CFCs) released at ground level move up to the stratosphere, where UV rays act on them and release Cl atoms. Cl degrades ozone, releasing molecular oxygen: $Cl + O_3 \rightarrow ClO + O_2$, and then $ClO + O \rightarrow Cl + O_2$. The chlorine atom comes out unchanged and so acts only as a catalyst; one Cl atom can destroy a very large number of ozone molecules, which is why CFCs thin the ozone layer so permanently. Answer: (2) Cl.
118	Biological ClassificationFive kingdom classification	Class 11: Biological Classification	Single correctEasy
A easy single correct question on five kingdom classification, from Biological Classification. NCERT: Class 11: Biological Classification Prokaryotes (kingdom Monera) are the bacteria and cyanobacteria. Nostoc and Oscillatoria are cyanobacteria (blue-green algae) and Mycobacterium is a bacterium. Saccharomyces (yeast) is a unicellular fungus (Ascomycetes), with a nucleus and membrane-bound organelles, so it is a eukaryote. Answer: (3) Saccharomyces.
119	Cell: The Unit of LifeCell organelles	Class 11: Cell: The Unit of Life	Single correctEasy
A easy single correct question on cell organelles, from Cell: The Unit of Life. NCERT: Class 11: Cell: The Unit of Life Materials to be packaged reach the cis (forming) face of the Golgi apparatus from the ER, are modified as they move through the cisternae, and leave from the trans (maturing) face as vesicles. The Golgi apparatus is thus the main site of packaging of materials to be delivered inside the cell or secreted outside it, and it forms secretory vesicles (it is also where glycoproteins and glycolipids are formed). Bacteria have no Golgi complex; fatty acids are broken down in mitochondria and peroxisomes; amino acids are activated in the cytoplasm by aminoacyl-tRNA synthetases. Answer: (2).
120	Photosynthesis in Higher PlantsLight reaction	Class 11: Photosynthesis in Higher Plants	Single correctEasy
A easy single correct question on light reaction, from Photosynthesis in Higher Plants. NCERT: Class 11: Photosynthesis in Higher Plants The light reactions (photochemical phase) include light absorption, splitting of water, oxygen release, and formation of the high-energy chemical intermediates ATP and NADPH. The products are therefore ATP, NADPH and O$_2$. NADH is formed in respiration (glycolysis and the Krebs cycle), not in photosynthesis. Answer: (2) NADH.
121	Cell: The Unit of LifeNucleus	Class 11: Cell: The Unit of Life	Single correctEasy
A easy single correct question on nucleus, from Cell: The Unit of Life. NCERT: Class 11: Cell: The Unit of Life The nucleolus is a spherical structure in the nucleoplasm. It is not membrane-bound: its content is continuous with the rest of the nucleoplasm. It is the site of active ribosomal RNA synthesis. Larger and more numerous nucleoli are present in cells actively carrying out protein synthesis (not simply in dividing cells; in fact the nucleolus disappears during prophase). The spindle is formed by the centrioles/microtubules, not the nucleolus. Answer: (4).
122	Transport in PlantsWater movement in plants	No matching NCERT chapter	Single correctMedium
A medium single correct question on water movement in plants, from Transport in Plants. NCERT: No matching NCERT chapter The opening and closing of stomata depends on the turgor of the guard cells, and the external factors that change it are those that affect transpiration and photosynthesis: light (stomata usually open in light), temperature, CO$_2$ concentration (a high internal CO$_2$ closes them) and water availability. Oxygen concentration has no recognised effect on stomatal movement. Answer: (1) O$_2$ concentration.
123	Cell Cycle and Cell DivisionMeiosis	Class 11: Cell Cycle and Cell Division	Single correctMedium
A medium single correct question on meiosis, from Cell Cycle and Cell Division. NCERT: Class 11: Cell Cycle and Cell Division In prophase I of meiosis: - Zygotene: homologous chromosomes pair (synapsis) and the synaptonemal complex forms. - Pachytene: crossing over takes place between non-sister chromatids. - Diplotene: the synaptonemal complex dissolves and the recombined homologous chromosomes of the bivalents begin to separate from each other, except at the sites of crossover (the X-shaped chiasmata). - Diakinesis: the chiasmata terminalise and the nuclear envelope breaks down. So the separation of the paired homologues begins in diplotene. Answer: (2) Diplotene.
124	Anatomy of Flowering PlantsTissue systems	Class 11: Anatomy of Flowering Plants	Single correctEasy
A easy single correct question on tissue systems, from Anatomy of Flowering Plants. NCERT: Class 11: Anatomy of Flowering Plants In most dicots the two guard cells of a stoma are bean (kidney) shaped. In grasses (Gramineae) the guard cells are dumb-bell shaped: narrow in the middle and swollen at the ends. They are accompanied by subsidiary cells in the epidermal tissue system. Answer: (3) Dumb-bell shaped.
125	Anatomy of Flowering PlantsSecondary growth	Class 11: Anatomy of Flowering Plants	Single correctEasy
A easy single correct question on secondary growth, from Anatomy of Flowering Plants. NCERT: Class 11: Anatomy of Flowering Plants In a dicot stem the intrafascicular cambium and the interfascicular cambium join to form a continuous ring of vascular cambium. It cuts off cells on both sides: towards the inside (pith side) it forms secondary xylem, and towards the outside it forms secondary phloem. Phellogen (cork cambium) produces cork and secondary cortex; the apical and axillary meristems give primary growth and branches. Answer: (2) Vascular cambium.
126	Morphology of Flowering PlantsRoot, stem and leaf	Class 11: Morphology of Flowering Plants	Single correctEasy
A easy single correct question on root, stem and leaf, from Morphology of Flowering Plants. NCERT: Class 11: Morphology of Flowering Plants In plants such as Rhizophora growing in swampy, saline areas (mangroves, which are halophytes), many roots come out of the ground and grow vertically upwards. These pneumatophores help the roots to get oxygen for respiration, since the waterlogged soil is poorly aerated. Answer: (3) Halophytes.
127	Anatomy of Flowering PlantsAnatomy of root, stem and leaf	Class 11: Anatomy of Flowering Plants	Single correctEasy
A easy single correct question on anatomy of root, stem and leaf, from Anatomy of Flowering Plants. NCERT: Class 11: Anatomy of Flowering Plants The innermost layer of the cortex is the endodermis, a single layer of barrel-shaped cells without intercellular spaces. The tangential as well as radial walls of the endodermal cells have a deposition of water-impermeable, waxy suberin in the form of Casparian strips. They block the apoplastic movement of water into the stele. Answer: (4) Endodermis.
128	Anatomy of Flowering PlantsSecondary growth	Class 11: Anatomy of Flowering Plants	Single correctEasy
A easy single correct question on secondary growth, from Anatomy of Flowering Plants. NCERT: Class 11: Anatomy of Flowering Plants Secondary growth needs a vascular cambium. Gymnosperms (conifers and cycads) and dicot angiosperms (including deciduous trees) have cambium and form secondary xylem and phloem. Monocots such as grasses have closed vascular bundles with no cambium, so they generally show no secondary growth. Answer: (3) Grasses.
129	Morphology of Flowering PlantsRoot, stem and leaf	Class 11: Morphology of Flowering Plants	Single correctEasy
A easy single correct question on root, stem and leaf, from Morphology of Flowering Plants. NCERT: Class 11: Morphology of Flowering Plants Roots of some plants change their shape and structure to store food. The tap roots of carrot and turnip and the adventitious roots of sweet potato are swollen and store food. (Potato, by contrast, is a stem tuber, and ginger a rhizome.) Answer: (2) Adventitious root.
130	Plant KingdomGymnosperms	Class 11: Plant Kingdom	Single correctMedium
A medium single correct question on gymnosperms, from Plant Kingdom. NCERT: Class 11: Plant Kingdom (1) Wrong. Horsetails (Equisetum) are pteridophytes. (2) Wrong. Selaginella and Salvinia are both heterosporous; Salvinia is a heterosporous water fern. (3) Correct. Gymnosperms (gymnos: naked, sperma: seeds) have ovules that are not enclosed by any ovary wall and remain exposed before and after fertilisation. (4) Wrong. The stem is unbranched in Cycas but branched in Pinus and Cedrus. Answer: (3).
131	Biological ClassificationMonera and Protista	Class 11: Biological Classification	Single correctMedium
A medium single correct question on monera and protista, from Biological Classification. NCERT: Class 11: Biological Classification (1) Wrong. Pseudopodia (false feet) are the locomotory and food-capturing structures of the amoeboid protozoans (e.g. Amoeba). Sporozoans (e.g. Plasmodium) are infectious spore-formers with no locomotory organelles. (2) Right. Mushrooms (Agaricus) are Basidiomycetes. (3) Right. Fungi have a cell wall of chitin and plants a cell wall of cellulose. (4) Right. Monera are prokaryotes without membrane-bound organelles such as mitochondria; in the other four kingdoms mitochondria are the site of aerobic respiration. Answer: (1).
132	Biological ClassificationFungi	Class 11: Biological Classification	Single correctMedium
A medium single correct question on fungi, from Biological Classification. NCERT: Class 11: Biological Classification In Basidiomycetes such as Agaricus (mushroom), karyogamy and meiosis take place in the basidium, and four basidiospores are produced exogenously, on the outside of the basidium. Neurospora and Saccharomyces are Ascomycetes: after karyogamy and meiosis the ascospores are produced endogenously, inside sac-like asci. Alternaria is a Deuteromycete: its sexual stage is unknown and it reproduces only by asexual conidia. Answer: (1) Agaricus.
133	The Living WorldTaxonomical aids	Class 11: The Living World	MatchingEasy
A easy matching question on taxonomical aids, from The Living World. NCERT: Class 11: The Living World a. A herbarium is a store-house of plant specimens that are dried, pressed and preserved on sheets (iii). b. A key is a taxonomical aid based on contrasting characters, generally in pairs (couplets), used to identify plants and animals (iv). c. A museum has collections of preserved plant and animal specimens for study and reference (i). d. A catalogue lists the species methodically with brief descriptions aiding identification (ii). So a-iii, b-iv, c-i, d-ii. Answer: (4).
134	Plant KingdomGymnosperms	Class 11: Plant Kingdom	Single correctEasy
A easy single correct question on gymnosperms, from Plant Kingdom. NCERT: Class 11: Plant Kingdom The pollen grains of Pinus have two air sacs (wings) formed by the exine. They make the pollen light and help in its dispersal by wind, since gymnosperms are wind-pollinated. Cycas pollen has no wings, and mango and mustard are insect-pollinated angiosperms with ordinary pollen. Answer: (4) Pinus.
135	Plant KingdomAlgae	Class 11: Plant Kingdom	Single correctMedium
A medium single correct question on algae, from Plant Kingdom. NCERT: Class 11: Plant Kingdom (1) Right. Marchantia, a liverwort, reproduces asexually by gemmae formed in gemma cups on the thallus. (2) Right. Brown algae (Phaeophyceae) reproduce asexually by biflagellate, pear-shaped zoospores with two unequal laterally attached flagella. (3) Wrong. Polysiphonia is a red alga (Rhodophyceae). Red algae have no flagellated stages at all: their asexual spores and gametes are non-motile, and sexual reproduction is oogamous. (4) Right. Chlorella is a unicellular green alga. Answer: (3).
147	Biological ClassificationMonera and Protista	Class 11: Biological Classification	Single correctEasy
A easy single correct question on monera and protista, from Biological Classification. NCERT: Class 11: Biological Classification Ciliated protozoans (e.g. Paramoecium) have two types of nuclei: a large macronucleus that controls the everyday working of the cell and a small micronucleus involved in reproduction. No other protozoan group has this nuclear dimorphism. Pseudopodia are used by amoeboid protozoans, flagella by flagellates, and contractile vacuoles are found in freshwater protozoans of several groups. Answer: (4).
152	Biological ClassificationMonera and Protista	Class 11: Biological Classification	Single correctEasy
A easy single correct question on monera and protista, from Biological Classification. NCERT: Class 11: Biological Classification Chrysophytes include diatoms and golden algae (desmids). Diatoms are microscopic, float passively in water currents (plankton), and photosynthesise in enormous numbers; they are the chief 'producers' in the oceans. Their siliceous cell walls accumulated over millions of years form diatomaceous earth. Answer: (2) Diatoms.
153	Organisms and PopulationsInteractions	Class 12: Organisms and Populations	Single correctMedium
A medium single correct question on interactions, from Organisms and Populations. NCERT: Class 12: Organisms and Populations Antibiotics are chemicals produced by some microbes that kill or retard the growth of other microbes. Penicillium, for example, secretes penicillin, which inhibits the growth of bacteria while Penicillium itself is neither benefited nor harmed by the bacteria. An interaction in which one species is harmed and the other is unaffected (– , 0) is amensalism. Antibiotic production exploits exactly this interaction. Answer: (4) Amensalism.
154	Biodiversity and ConservationConservation strategies	Class 12: Biodiversity and Conservation	Single correctEasy
A easy single correct question on conservation strategies, from Biodiversity and Conservation. NCERT: Class 12: Biodiversity and Conservation Ex situ (off-site) conservation takes threatened plants and animals out of their natural habitat and protects them in special settings: zoological parks, botanical gardens, wildlife safari parks, and cryopreservation in seed banks and gene banks. Sacred groves are tracts of forest set aside and protected by local communities on religious grounds, in their natural habitat, so they are in situ conservation. Answer: (2) Sacred groves.
155	Environmental IssuesOzone depletion	No matching NCERT chapter	MatchingEasy
A easy matching question on ozone depletion, from Environmental Issues. NCERT: No matching NCERT chapter a. Eutrophication is the natural ageing of a lake by nutrient enrichment of its water (iii). b. Sanitary landfills, in which wastes are dumped in a depression and covered with dirt every day, are a method of solid waste disposal (iv). c. A high dose of UV-B inflames the cornea, causing snow blindness and cataract (i). d. Jhum (slash and burn) cultivation in north-eastern India clears forest by felling and burning trees, so it causes deforestation (ii). So a-iii, b-iv, c-i, d-ii. Answer: (1).
156	Organisms and PopulationsPopulation attributes	Class 12: Organisms and Populations	Single correctEasy
A easy single correct question on population attributes, from Organisms and Populations. NCERT: Class 12: Organisms and Populations When the numbers of pre-reproductive, reproductive and post-reproductive individuals are plotted, the shape of the age pyramid shows the growth status of the population. A growing (expanding) population has a broad base, a triangular pyramid: the pre-reproductive individuals outnumber the reproductive ones. A stable population has a bell shape (pre-reproductive about equal to reproductive), and a declining one an urn shape (fewer pre-reproductive individuals). Answer: (3).
158	Molecular Basis of InheritanceLac operon	Class 12: Molecular Basis of Inheritance	Single correctEasy
A easy single correct question on lac operon, from Molecular Basis of Inheritance. NCERT: Class 12: Molecular Basis of Inheritance An operon is the prokaryotic arrangement in which a set of structural genes is controlled together by a common promoter and operator (the lac operon has the structural genes z, y, a, with the promoter and operator, under the control of the regulator gene i). An enhancer is a regulatory DNA sequence of eukaryotic genes, which may lie far from the promoter; it is not part of an operon. Answer: (1) an enhancer.
159	Principles of Inheritance and VariationGenetic disorders	Class 12: Principles of Inheritance and Variation	Single correctEasy
A easy single correct question on genetic disorders, from Principles of Inheritance and Variation. NCERT: Class 12: Principles of Inheritance and Variation A mother passes one of her two X chromosomes to every child, son or daughter alike: sons get their X from the mother and Y from the father, and daughters one X from each parent. So the X chromosome carrying the condition has an equal (1/2) chance of going to each son and each daughter. (It is the father whose X goes only to daughters.) Answer: (4) Both sons and daughters.
161	Molecular Basis of InheritanceTranscription and translation	Class 12: Molecular Basis of Inheritance	Single correctEasy
A easy single correct question on transcription and translation, from Molecular Basis of Inheritance. NCERT: Class 12: Molecular Basis of Inheritance The mRNA is made complementary to the template strand, which is itself complementary to the coding strand. So the mRNA has the same sequence (and the same 5'→3' polarity) as the coding strand, except that uracil replaces thymine. Coding strand: AGGTATCGCAT mRNA: AGGUAUCGCAU Option (2) still has T, and options (1) and (4) are complementary sequences. Answer: (3).
170	Respiration in PlantsETS and oxidative phosphorylation	Class 11: Respiration in Plants	Single correctEasy
A easy single correct question on ets and oxidative phosphorylation, from Respiration in Plants. NCERT: Class 11: Respiration in Plants (1) Right. In glycolysis, glyceraldehyde-3-phosphate is oxidised with NAD$^+$ accepting the hydrogen; glycolysis can continue only as long as NAD$^+$ is regenerated (by the ETS aerobically or by fermentation). (2) Right. Glycolysis takes place in the cytoplasm of all living organisms. (3) Right. The TCA (Krebs) cycle enzymes are in the mitochondrial matrix (succinate dehydrogenase, the exception, is on the inner membrane). (4) Wrong. The electron transport system and ATP synthase (complex V) are located in the inner mitochondrial membrane, so oxidative phosphorylation takes place there, not in the outer membrane. Answer: (4).
171	Cell: The Unit of LifeNucleus	Class 11: Cell: The Unit of Life	Single correctMedium
A medium single correct question on nucleus, from Cell: The Unit of Life. NCERT: Class 11: Cell: The Unit of Life (1) Right. A submetacentric chromosome has its centromere slightly away from the middle, giving one shorter and one longer arm, so it appears L-shaped at anaphase. (2) Right. Allosomes are the sex chromosomes (the rest are autosomes). (3) Right. Lampbrush chromosomes are giant, highly extended bivalents seen in the diplotene stage of meiosis I in oocytes. (4) Wrong. The lampbrush chromosomes are the ones found in the oocytes of amphibians. Polytene chromosomes are found in the salivary gland cells of insect larvae (e.g. Drosophila, Chironomus); they are formed by repeated replication of DNA without cell division. Answer: (4).
173	Cell: The Unit of LifeCell organelles	Class 11: Cell: The Unit of Life	Single correctMedium
A medium single correct question on cell organelles, from Cell: The Unit of Life. NCERT: Class 11: Cell: The Unit of Life The rough ER, studded with ribosomes, is the site of synthesis of secretory and membrane proteins. As the polypeptide enters the ER lumen, its signal peptide is cleaved off, and the protein is folded and given its initial (N-linked) glycosylation there. The smooth endoplasmic reticulum is the major site for synthesis of lipids, including phospholipids and, in animal cells, steroidal hormones. So phospholipid synthesis is the event that does not take place in the RER. Answer: (4) Phospholipid synthesis.
174	Molecular Basis of InheritanceTranscription and translation	Class 12: Molecular Basis of Inheritance	Single correctEasy
A easy single correct question on transcription and translation, from Molecular Basis of Inheritance. NCERT: Class 12: Molecular Basis of Inheritance Several ribosomes may attach to one mRNA and translate it at the same time, each making a copy of the polypeptide. Such a chain of ribosomes on an mRNA is called a polyribosome or polysome. A nucleosome is the unit of DNA wrapped around a histone octamer; plastidome means all the plastids of a cell; polyhedral bodies are not ribosomal. Answer: (3) Polysome.
178	Microbes in Human WelfareMicrobes in household products	Class 12: Microbes in Human Welfare	Single correctEasy
A easy single correct question on microbes in household products, from Microbes in Human Welfare. NCERT: Class 12: Microbes in Human Welfare Lactic acid bacteria (LAB) such as Lactobacillus grow in milk and convert it to curd: the acid they produce coagulates and partially digests the milk proteins. LAB also improve the nutritional quality of curd by increasing vitamin B$_{12}$, and in the stomach they check disease-causing microbes. Answer: (1) Vitamin B$_{12}$.
180	Principles of Inheritance and VariationDeviations from Mendelism	Class 12: Principles of Inheritance and Variation	StatementsEasy
A easy statements question on deviations from mendelism, from Principles of Inheritance and Variation. NCERT: Class 12: Principles of Inheritance and Variation The ABO blood group is controlled by a single gene I with three alleles, I$^A$, I$^B$ and i: - Multiple alleles (c): three alleles of one gene exist in the population. - Dominance (a): I$^A$ and I$^B$ are each dominant over i (I$^A$i gives group A, I$^B$i gives B). - Co-dominance (b): when I$^A$ and I$^B$ are together, both are expressed, giving group AB. It is a single-gene trait, so it is not polygenic (e), and no allele shows incomplete dominance (d). So the characteristics are a, b and c. Answer: (2).

Zoology questions, each with its chapter and our explanation
Q	Chapter and topic	NCERT	Kind and level
98	Biotechnology and its ApplicationsGene therapy	Class 12: Biotechnology and its Applications	Single correctEasy
A easy single correct question on gene therapy, from Biotechnology and its Applications. NCERT: Class 12: Biotechnology and its Applications In the first clinical gene therapy (1990, a 4-year-old girl with ADA deficiency), lymphocytes from the patient's blood were grown in culture, and a functional ADA cDNA was introduced into them using a retroviral vector; the cells were then returned to the patient. Disarmed retroviruses are used to deliver genes into animal (including human) cells because they integrate their DNA into the host genome. $\lambda$ phage and pBR322 are vectors for bacteria (E. coli), and the Ti plasmid of Agrobacterium tumefaciens is a vector for plant cells. Answer: (3) Retrovirus.
99	Biotechnology and its ApplicationsBiosafety, biopiracy and patents	Class 12: Biotechnology and its Applications	Single correctEasy
A easy single correct question on biosafety, biopiracy and patents, from Biotechnology and its Applications. NCERT: Class 12: Biotechnology and its Applications Biopiracy is the term used for the use of bio-resources (and the traditional knowledge about them) by multinational companies and other organisations without proper authorisation from the countries and people concerned and without compensatory payment. Biodegradation is the breakdown of matter by microbes; the other two are not the standard term. Answer: (2) Biopiracy.
100	Biotechnology and its ApplicationsBiosafety, biopiracy and patents	Class 12: Biotechnology and its Applications	Single correctEasy
A easy single correct question on biosafety, biopiracy and patents, from Biotechnology and its Applications. NCERT: Class 12: Biotechnology and its Applications The Indian Government has set up the Genetic Engineering Approval (Appraisal) Committee, GEAC, which makes decisions regarding the validity of GM research and the safety of introducing GM organisms for public services. (RCGM reviews research projects in laboratories; CSIR and ICMR are research councils.) Answer: (4) GEAC.
101	Biotechnology: Principles and ProcessesPCR and bioreactors	Class 12: Biotechnology: Principles and Processes	Single correctEasy
A easy single correct question on pcr and bioreactors, from Biotechnology: Principles and Processes. NCERT: Class 12: Biotechnology: Principles and Processes Each PCR cycle has three steps in this order: 1. Denaturation: heating separates the two strands of the double-stranded template DNA. 2. Annealing: on cooling, the two primers (small chemically synthesised oligonucleotides) pair with the complementary regions of the single strands. 3. Extension: the thermostable DNA polymerase (Taq polymerase) extends the primers using the nucleotides provided, copying the region between them. The cycle is then repeated many times. Answer: (4) Denaturation, Annealing, Extension.
103	Biotechnology and its ApplicationsBiosafety, biopiracy and patents	Class 12: Biotechnology and its Applications	Single correctEasy
A easy single correct question on biosafety, biopiracy and patents, from Biotechnology and its Applications. NCERT: Class 12: Biotechnology and its Applications In 1997 an American company got patent rights on Basmati rice through the US Patent and Trademark Office. The 'new' variety had in fact been derived from Indian farmers' varieties: Indian Basmati was crossed with semi-dwarf varieties and claimed as an invention. This is a well-known case of biopiracy. Lerma Rojo and Sharbati Sonora are wheat varieties and Co-667 is a sugarcane variety. Answer: (4) Basmati.
117	BiomoleculesCarbohydrates, lipids and nucleic acids	Class 11: Biomolecules	Single correctEasy
A easy single correct question on carbohydrates, lipids and nucleic acids, from Biomolecules. NCERT: Class 11: Biomolecules Sugars (carbohydrates) are polyhydroxy aldehydes or ketones. Glucose, for example, has an aldehyde group (–CHO, a carbonyl) at C-1 and hydroxyl groups (–OH) on the other carbons; fructose has a keto group (C=O) and hydroxyl groups. So the characteristic groups are carbonyl and hydroxyl. Phosphate is found in nucleotides and phospholipids, and methyl is not a defining group of sugars. Answer: (4) carbonyl and hydroxyl.
136	Breathing and Exchange of GasesRespiratory disorders	Class 11: Breathing and Exchange of Gases	Single correctEasy
A easy single correct question on respiratory disorders, from Breathing and Exchange of Gases. NCERT: Class 11: Breathing and Exchange of Gases Asthma is a difficulty in breathing causing wheezing, due to inflammation of the bronchi and bronchioles. Emphysema is a chronic disorder in which the alveolar walls are damaged, so the respiratory surface is decreased; cigarette smoking is one of its major causes. So the order asthma; emphysema is inflammation of bronchioles; decreased respiratory surface. Answer: (3).
137	Body Fluids and CirculationCardiac cycle	Class 11: Body Fluids and Circulation	MatchingEasy
A easy matching question on cardiac cycle, from Body Fluids and Circulation. NCERT: Class 11: Body Fluids and Circulation a. The opening between the right atrium and the right ventricle is guarded by a valve of three muscular flaps or cusps, the tricuspid valve (iii). b. The bicuspid (mitral) valve guards the opening between the left atrium and the left ventricle (i). c. The openings of the right and left ventricles into the pulmonary artery and the aorta are guarded by the semilunar valves (ii). So a-iii, b-i, c-ii. Answer: (3).
138	Breathing and Exchange of GasesMechanism and regulation of breathing	Class 11: Breathing and Exchange of Gases	MatchingMedium
A medium matching question on mechanism and regulation of breathing, from Breathing and Exchange of Gases. NCERT: Class 11: Breathing and Exchange of Gases The textbook values for a healthy adult: a. Tidal volume, the air inspired or expired during normal breathing: about 500 mL (iii). b. Inspiratory reserve volume, the extra air that can be inspired by a forcible inspiration: 2500–3000 mL (i). c. Expiratory reserve volume, the extra air that can be expired by a forcible expiration: 1000–1100 mL (iv). d. Residual volume, the air that remains in the lungs even after a forcible expiration: 1100–1200 mL (ii). So a-iii, b-i, c-iv, d-ii. Answer: (2).
139	Neural Control and CoordinationSense organs	Class 11: Neural Control and Coordination	Single correctEasy
A easy single correct question on sense organs, from Neural Control and Coordination. NCERT: Class 11: Neural Control and Coordination The ciliary body is the forward continuation of the choroid, and the iris continues in front of it. Behind the iris lies the transparent crystalline lens, which is held in place by ligaments (suspensory ligaments) attached to the ciliary body. The smooth muscles of the ciliary body change the tension on these ligaments to alter the curvature of the lens, while the muscles of the iris control the size of the pupil. Answer: (3).
140	Chemical Coordination and IntegrationHormone mechanism	Class 11: Chemical Coordination and Integration	Single correctEasy
A easy single correct question on hormone mechanism, from Chemical Coordination and Integration. NCERT: Class 11: Chemical Coordination and Integration By chemical nature, hormones are peptides/proteins (insulin, glucagon), steroids (cortisol, testosterone, estradiol, progesterone), iodothyronines (thyroid hormones), and amino-acid derivatives (epinephrine). Epinephrine (adrenaline) is a catecholamine made from the amino acid tyrosine. Estradiol and estriol are steroid estrogens, and ecdysone, the insect moulting hormone, is also a steroid. Answer: (3) Epinephrine.
141	Locomotion and MovementJoints and disorders	Class 11: Locomotion and Movement	Single correctMedium
A medium single correct question on joints and disorders, from Locomotion and Movement. NCERT: Class 11: Locomotion and Movement Osteoporosis is an age-related disorder of decreased bone mass and increased chances of fractures. Decreased levels of estrogen are a common cause (hence its frequency in women after menopause). Parathyroid hormone raises blood Ca$^{2+}$ by stimulating bone resorption (demineralisation), so an excess of it also thins the bones. Progesterone, aldosterone and prolactin have no such direct role in bone mass. Answer: (1) Estrogen and Parathyroid hormone.
142	Neural Control and CoordinationCentral nervous system	Class 11: Neural Control and Coordination	Single correctMedium
A medium single correct question on central nervous system, from Neural Control and Coordination. NCERT: Class 11: Neural Control and Coordination (1) Right. The hypothalamus has centres that control body temperature and the urge for eating and drinking, and it secretes the releasing (and inhibiting) hormones. (2) Wrong. The limbic system (limbic lobe) is formed by the inner parts of the cerebral hemispheres with deep structures such as the amygdala and hippocampus. Along with the hypothalamus it regulates sexual behaviour, emotional reactions (excitement, pleasure, rage, fear) and motivation. It is not a set of fibre tracts interconnecting brain regions, and it does not control movement. (3) Right. The medulla has centres controlling respiration, cardiovascular reflexes and gastric secretions. (4) Right. The two cerebral hemispheres are connected by a tract of nerve fibres, the corpus callosum. Answer: (2).
143	Human ReproductionEmbryonic development	Class 12: Human Reproduction	Single correctHard
A hard single correct question on embryonic development, from Human Reproduction. NCERT: Class 12: Human Reproduction The extra-embryonic membranes are made of two germ layers each. The amnion (like the chorion) is formed from ectoderm on the inside together with the somatic layer of extra-embryonic mesoderm on the outside; this ectoderm–somatic mesoderm combination is called somatopleure. The yolk sac and allantois are formed from endoderm with splanchnic mesoderm (splanchnopleure). So the amnion is derived from ectoderm and mesoderm. Answer: (3).
144	Human ReproductionEmbryonic development	Class 12: Human Reproduction	Single correctEasy
A easy single correct question on embryonic development, from Human Reproduction. NCERT: Class 12: Human Reproduction The placenta acts as an endocrine tissue and produces human chorionic gonadotropin (hCG), human placental lactogen (hPL), estrogens and progestogens. These maintain pregnancy. Relaxin is secreted by the ovary in the later phase of pregnancy; oxytocin comes from the posterior pituitary; prolactin from the anterior pituitary; glucocorticoids from the adrenal cortex. Answer: (1) hCG, hPL, progestogens, estrogens.
145	Human ReproductionGametogenesis	Class 12: Human Reproduction	Single correctEasy
A easy single correct question on gametogenesis, from Human Reproduction. NCERT: Class 12: Human Reproduction In spermatogenesis, secondary spermatocytes complete meiosis II to form haploid spermatids. The spermatids are transformed into spermatozoa (sperms) by spermiogenesis. After spermiogenesis, the sperm heads are embedded in the Sertoli cells, and they are finally released from the seminiferous tubules by the process called spermiation. So spermiogenesis forms spermatozoa, and spermiation releases them from the Sertoli cells into the lumen (cavity) of the seminiferous tubule. Answer: (4).
146	Reproductive HealthContraception	Class 12: Reproductive Health	Single correctMedium
A medium single correct question on contraception, from Reproductive Health. NCERT: Class 12: Reproductive Health Saheli is an oral contraceptive pill for females, developed at the Central Drug Research Institute (CDRI), Lucknow. It contains a non-steroidal preparation (centchroman) and is taken once a week. It is not an IUD and not a post-coital (emergency) pill. Centchroman acts as an anti-estrogen: it blocks estrogen receptors in the uterus, so the endometrium is not made ready in time and the fertilised egg cannot get implanted. It does not raise estrogen levels or suppress ovulation. Answer: (3).
148	Animal KingdomChordate classes	Class 11: Animal Kingdom	Single correctEasy
A easy single correct question on chordate classes, from Animal Kingdom. NCERT: Class 11: Animal Kingdom In birds (class Aves) the digestive tract has additional chambers: the crop, which stores food, and the gizzard, a muscular grinding chamber that makes up for the absence of teeth. Reptiles, amphibians and bony fishes have no crop and gizzard. Answer: (1) Aves.
149	Structural Organisation in AnimalsCockroach morphology and anatomy	Class 11: Structural Organisation in Animals	Single correctMedium
A medium single correct question on cockroach morphology and anatomy, from Structural Organisation in Animals. NCERT: Class 11: Structural Organisation in Animals In both sexes the 10th abdominal segment bears a pair of jointed filamentous anal cerci, and both have forewings modified as tegmina, so these do not separate the sexes. In females the 7th sternum is boat-shaped and, together with the 8th and 9th sterna, forms a brood or genital pouch. Only males bear a pair of short, thread-like anal (caudal) styles on the 9th abdominal segment. So the presence of caudal styles identifies a male. Answer: (2).
150	Animal KingdomChordate classes	Class 11: Animal Kingdom	Single correctEasy
A easy single correct question on chordate classes, from Animal Kingdom. NCERT: Class 11: Animal Kingdom Birds and mammals are homeotherms (warm-blooded): they maintain a constant body temperature. Camelus (camel) and Macropus (kangaroo) are mammals, and Psittacula (parrot) is a bird. Chelone (turtle) is a reptile, and reptiles are poikilotherms (cold-blooded), lacking the capacity to regulate their body temperature. Answer: (2) Chelone.
151	Animal KingdomNon-chordate phyla	Class 11: Animal Kingdom	Single correctMedium
A medium single correct question on non-chordate phyla, from Animal Kingdom. NCERT: Class 11: Animal Kingdom Metamorphosis is the change from a larval form into the adult. Moths (insects) have a caterpillar larva that becomes a pupa and then the adult. The tunicate larva is a free-swimming tadpole-like form with a notochord in the tail, which settles and changes into the sessile adult. Echinoderms such as starfish have bilaterally symmetrical larvae that change into radially symmetrical adults. In the earthworm, fertilisation and development take place within a cocoon and development is direct: no larval stage is formed, so there is no metamorphosis. Answer: (3) Earthworm.
157	Human Health and DiseaseCancer and drug abuse	Class 12: Human Health and Disease	Single correctEasy
A easy single correct question on cancer and drug abuse, from Human Health and Disease. NCERT: Class 12: Human Health and Disease Opioids are obtained from the poppy plant Papaver somniferum. Morphine is extracted from the latex of the plant (the milky juice from the unripe capsules). Heroin, commonly called smack, is chemically diacetylmorphine, obtained by acetylation of morphine. So smack comes ultimately from the latex. Answer: (2) Latex.
160	EvolutionEvidences of evolution	Class 12: Evolution	Single correctEasy
A easy single correct question on evidences of evolution, from Evolution. NCERT: Class 12: Evolution Working on the evening primrose (Oenothera lamarckiana), Hugo de Vries proposed that evolution is caused by mutation, not by the minor continuous variations Darwin emphasised. Mutations are large, sudden and random, and a single-step large mutation produces a new species. He called this single-step large mutation saltation. Answer: (2) Saltation.
162	Human ReproductionMenstrual cycle	Class 12: Human Reproduction	MatchingEasy
A easy matching question on menstrual cycle, from Human Reproduction. NCERT: Class 12: Human Reproduction a. In the follicular phase the primary follicles grow into a Graafian follicle and, under estrogen, the endometrium regenerates by proliferation; so the proliferative phase is the follicular phase (ii). b. In the luteal phase the corpus luteum secretes progesterone, which makes the endometrium secretory and ready for implantation; the secretory phase is the luteal phase (iii). c. Menstruation is the breakdown of the endometrial lining and its blood vessels, which leaves as menstrual flow (i). So a-ii, b-iii, c-i. Answer: (1).
163	Excretory Products and their EliminationRegulation and disorders	Class 11: Excretory Products and their Elimination	MatchingEasy
A easy matching question on regulation and disorders, from Excretory Products and their Elimination. NCERT: Class 11: Excretory Products and their Elimination a. Glycosuria is the presence of glucose in urine, as in diabetes mellitus (iv). b. Gout is inflammation of joints due to accumulation of uric acid crystals (i). c. Renal calculi are stones or insoluble masses of crystallised salts (oxalates etc.) formed within the kidney (ii). d. Glomerulonephritis is inflammation of the glomeruli of the kidney (iii). So a-iv, b-i, c-ii, d-iii. Answer: (4).
164	Excretory Products and their EliminationUrine formation	Class 11: Excretory Products and their Elimination	MatchingEasy
A easy matching question on urine formation, from Excretory Products and their Elimination. NCERT: Class 11: Excretory Products and their Elimination a. Ultrafiltration of blood through the glomerular capillaries into Bowman's capsule takes place in the Malpighian corpuscle (renal corpuscle: glomerulus with Bowman's capsule) (iv). b. The Henle's loop, by the counter-current mechanism, maintains the high osmolarity of the medullary interstitial fluid, which allows urine to be concentrated (i). c. The ureters carry urine from the kidneys to the bladder (ii). d. Urine is stored in the urinary bladder until micturition (iii). The proximal convoluted tubule (v), the main site of reabsorption, is not needed. So a-iv, b-i, c-ii, d-iii. Answer: (2).
165	Digestion and AbsorptionHuman digestive system	No matching NCERT chapter	Single correctMedium
A medium single correct question on human digestive system, from Digestion and Absorption. NCERT: No matching NCERT chapter The gastric glands have three kinds of cells: mucus neck cells (mucus), peptic or chief cells (pepsinogen), and parietal or oxyntic cells (HCl and Castle's intrinsic factor). Intrinsic factor is essential for the absorption of vitamin B$_{12}$ in the ileum, and vitamin B$_{12}$ is needed for the maturation of red blood cells (erythropoiesis); without it pernicious anaemia results. So the parietal cells help erythropoiesis indirectly. Answer: (4) Parietal cells.
166	Body Fluids and CirculationBlood composition	Class 11: Body Fluids and Circulation	MatchingEasy
A easy matching question on blood composition, from Body Fluids and Circulation. NCERT: Class 11: Body Fluids and Circulation The major plasma proteins and their roles: a. Fibrinogen is needed for clotting or coagulation of blood (ii). b. Globulins are involved primarily in the defence mechanisms of the body (antibodies) (iii). c. Albumins help in osmotic balance (i). So a-ii, b-iii, c-i. Answer: (4).
167	Breathing and Exchange of GasesRespiratory disorders	Class 11: Breathing and Exchange of Gases	Single correctEasy
A easy single correct question on respiratory disorders, from Breathing and Exchange of Gases. NCERT: Class 11: Breathing and Exchange of Gases Occupational respiratory disorders arise from the work environment. In industries involving grinding or stone-breaking, so much dust is produced that the body's defences cannot cope; long exposure causes inflammation and fibrosis of the upper lung and serious lung damage. Silicosis (and asbestosis) are such disorders. Botulism is food poisoning by a bacterial toxin, anthrax is a bacterial infection, and emphysema is caused mainly by cigarette smoking. Answer: (2) Silicosis.
168	Locomotion and MovementMuscle contraction	Class 11: Locomotion and Movement	Single correctEasy
A easy single correct question on muscle contraction, from Locomotion and Movement. NCERT: Class 11: Locomotion and Movement A neural signal releases Ca$^{2+}$ from the sarcoplasmic reticulum. The raised Ca$^{2+}$ binds to a subunit of troponin on the actin filaments, which removes the masking of the active sites for myosin. The myosin head, already energised by ATP hydrolysis, then binds to the exposed sites forming cross bridges, and pulls the actin filaments towards the centre of the A-band. ATP (not calcium) detaches the head, and calcium promotes rather than prevents cross-bridge formation. Answer: (3).
169	Neural Control and CoordinationNeuron and nerve impulse	Class 11: Neural Control and Coordination	Single correctMedium
A medium single correct question on neuron and nerve impulse, from Neural Control and Coordination. NCERT: Class 11: Neural Control and Coordination The cell body (cyton) of a neuron contains cytoplasm with typical cell organelles and certain granular bodies called Nissl's granules. These granules are clumps of rough endoplasmic reticulum with attached and free ribosomes; they stain deeply with basic dyes because of their rRNA, and they are the site of the neuron's protein synthesis. Answer: (4) Free ribosomes and RER.
172	Digestion and AbsorptionHuman digestive system	No matching NCERT chapter	Single correctEasy
A easy single correct question on human digestive system, from Digestion and Absorption. NCERT: No matching NCERT chapter Each human tooth is embedded in a socket of the jaw bone (thecodont). Most mammals, including humans, form two sets of teeth in life, temporary milk (deciduous) teeth replaced by permanent teeth (diphyodont). An adult has different types of teeth, incisors, canines, premolars and molars (heterodont). Answer: (2) Thecodont, Diphyodont, Heterodont.
175	Human Health and DiseasePathogens and diseases	Class 12: Human Health and Disease	Single correctEasy
A easy single correct question on pathogens and diseases, from Human Health and Disease. NCERT: Class 12: Human Health and Disease Filariasis (elephantiasis) is caused by filarial worms (Wuchereria bancrofti and W. malayi), which live in the lymphatic vessels, mostly of the lower limbs, and cause chronic inflammation of the organs in which they live for many years; the limbs and genital organs become grossly deformed. The pathogen is transmitted by the bite of female mosquito vectors. Ringworm is fungal and spreads by contact, while ascariasis and amoebiasis spread through contaminated food and water. Answer: (3) Elephantiasis.
176	Human Health and DiseaseImmunity	Class 12: Human Health and Disease	Single correctEasy
A easy single correct question on immunity, from Human Health and Disease. NCERT: Class 12: Human Health and Disease In an autoimmune disease the body's immune system attacks its own cells. Rheumatoid arthritis (attack on joint tissue), psoriasis (immune-driven skin inflammation) and vitiligo (destruction of melanocytes) are autoimmune. Alzheimer's disease is a neurodegenerative disorder caused by the loss of neurons in the brain (associated with a deficiency of acetylcholine), not by an immune attack on self. Answer: (1) Alzheimer's disease.
177	EvolutionEvidences of evolution	Class 12: Evolution	Single correctEasy
A easy single correct question on evidences of evolution, from Evolution. NCERT: Class 12: Evolution Divergent evolution gives homologous structures: organs with the same basic structure and common origin that come to perform different functions in different animals, such as the forelimbs, hearts and brains of vertebrates (bat, man, cheetah). The eye of the octopus (a mollusc) and the eyes of mammals perform the same function but are not of common origin; they are analogous, the result of convergent evolution. So the set with the octopus eye is not an example of divergent evolution. Answer: (4).
179	EvolutionEvidences of evolution	Class 12: Evolution	Single correctEasy
A easy single correct question on evidences of evolution, from Evolution. NCERT: Class 12: Evolution Whales, bats, cheetahs and humans share a similar anatomical pattern of forelimb bones (humerus, radius, ulna, carpals, metacarpals, phalanges), although the forelimbs perform different functions. Organs with the same structure and origin but different functions are homologous; their similarity points to common ancestry and results from divergent evolution. Analogy and convergent evolution refer to organs similar in function but different in structure and origin. Answer: (3) Homology.

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