p-Block Elements: NEET PYQ, 2018–2026

Q1 · Chemistry · p-Block Elements

Which of the following is the strongest acid in aqueous solution?

• AHF
• BHCl
• CHI
• DHBr

Q2 · Chemistry · p-Block Elements

Going down group 15 from NH₃ to BiH₃, the basic character of the hydrides:

• Adecreases
• Bincreases
• Cstays the same
• Dfirst increases and then decreases

Q3 · Chemistry · p-Block Elements

In the contact process, 2SO₂(g) + O₂(g) ⇌ 2SO₃(g) is exothermic (ΔH° = –196.6 kJ mol⁻¹). Plants use V₂O₅ at about 720 K and only about 2 bar, although lower temperature and higher pressure would each favour SO₃ at equilibrium. Which statement best explains this choice of conditions?

• ALower temperature would raise the equilibrium conversion but make the rate too slow. The conversion is already high at about 2 bar, so a much higher pressure is not worth its cost.
• BV₂O₅ shifts the equilibrium towards SO₃ only at high temperature, so about 720 K is needed to make the catalyst raise the equilibrium yield.
• CThe forward reaction is endothermic, so high temperature is needed to favour SO₃ and only a moderate pressure is needed to keep SO₂ from decomposing.
• DHigh pressure would favour SO₂ because the reaction produces fewer moles of gas, so a low pressure is used to push the equilibrium forward.

Q4 · Chemistry · p-Block Elements

Which of the following hydrides of group 15 is the strongest reducing agent?

• ANH₃
• BBiH₃
• CPH₃
• DSbH₃

Q5 · Chemistry · p-Block Elements

Sulphur has a much greater tendency for catenation (S–S chains and rings) than oxygen has (O–O chains). What is the main reason?

• AThe O–O single bond is weak because of strong lone pair–lone pair repulsion between the small oxygen atoms, whereas the S–S bond is stronger.
• BOxygen is more electronegative, so O–O bonds are more polar and hence break more readily than S–S bonds.
• CSulphur forms strong pπ–pπ multiple bonds with itself, which link the atoms into chains.
• DOxygen exists as a gas at room temperature, so it cannot form chains.

Q6 · Chemistry · p-Block Elements

In the solid state, phosphorus pentachloride exists as an ionic solid made of [PCl₄]⁺ and [PCl₆]⁻ ions, whereas in the gas phase it is a trigonal bipyramidal molecule. Which row correctly gives the shape and the hybridisation of phosphorus in the two solid-state ions?

• A[PCl₄]⁺ is tetrahedral (sp³) and [PCl₆]⁻ is octahedral (sp³d²)
• B[PCl₄]⁺ is see-saw (sp³d) and [PCl₆]⁻ is octahedral (sp³d²)
• C[PCl₄]⁺ is tetrahedral (sp³) and [PCl₆]⁻ is trigonal bipyramidal (sp³d)
• D[PCl₄]⁺ is square planar (dsp²) and [PCl₆]⁻ is octahedral (d²sp³)

Q7 · Chemistry · p-Block Elements

At room temperature water is a liquid while hydrogen sulphide is a gas, although H₂S has the higher molar mass. The reason is that:

• Athe O–H bond is weaker than the S–H bond
• Bwater molecules are held together by hydrogen bonds, which H₂S molecules do not form to any real extent
• Cwater molecules have stronger dispersion forces than H₂S molecules
• Doxygen has vacant d orbitals with which water molecules link together

Q8 · Chemistry · p-Block Elements

Which statement about the allotropes of sulphur is correct?

• AMonoclinic sulphur is the stable form at room temperature and changes to rhombic sulphur above 369 K.
• BRhombic and monoclinic sulphur both consist of S₈ molecules, but they differ in crystal packing, and rhombic sulphur is stable below 369 K.
• CRhombic sulphur contains S₈ rings, whereas monoclinic sulphur contains S₆ rings.
• DBoth forms contain planar S₈ rings, and they interconvert at 273 K.

Q9 · Chemistry · p-Block Elements

One mole of PCl₃ is hydrolysed completely by excess water, giving a phosphorus oxoacid and HCl. The resulting solution is then titrated with NaOH until every ionisable hydrogen of all the acids present has been neutralised. How many moles of NaOH are required?

• A3
• B4
• C5
• D6

Q10 · Chemistry · p-Block Elements

The boiling points of the noble gases rise steadily from helium to xenon because:

• Athe dispersion forces between the atoms become stronger as the atoms grow larger and more polarisable
• Bthe atoms form stronger covalent bonds with one another down the group
• Cthe ionisation enthalpy increases down the group
• Dthe heavier atoms are permanent dipoles that attract one another