Chemical Kinetics: JEE Main PYQ, 2020–2025

Q1 · Chemistry · Chemical Kinetics

Which of the following statements about the pre-exponential factor A in the Arrhenius equation k = A e^(−Ea/RT) is correct?

• AA is independent of the initial concentrations of the reactants.
• BA doubles whenever the initial concentration of each reactant is doubled.
• CA becomes zero when the activation energy is zero.
• DA depends on the activation energy, so a larger Ea gives a larger A.

Q2 · Chemistry · Chemical Kinetics

For a reaction A → products, a plot of log₁₀(rate) against log₁₀[A] is a straight line with slope 2. It cuts the log(rate) axis at −3.0, that is, at log₁₀[A] = 0. Concentration is in mol L⁻¹ and rate is in mol L⁻¹ s⁻¹. What is the rate of the reaction when [A] = 0.10 mol L⁻¹?

• A1.0 × 10⁻⁴ mol L⁻¹ s⁻¹
• B1.0 × 10⁻⁶ mol L⁻¹ s⁻¹
• C1.0 × 10⁻³ mol L⁻¹ s⁻¹
• D1.0 × 10⁻⁵ mol L⁻¹ s⁻¹

Q3 · Chemistry · Chemical Kinetics

The gas-phase reaction A(g) → 2B(g) is carried out at constant temperature in a rigid vessel, starting with pure A at a pressure of 0.40 atm. The total pressure in the vessel is 0.60 atm after 10 min and 0.70 atm after 20 min. Assuming the reaction follows simple zero-, first- or second-order kinetics in A, what is its order?

• AZero order
• BFirst order
• CSecond order
• DThe order cannot be determined, because the total pressure rather than the partial pressure of A is measured

Q4 · Chemistry · Chemical Kinetics

A reaction has a rate constant k whose units are L mol⁻¹ s⁻¹. What is the order of this reaction?

• AZero order
• BFirst order
• CSecond order
• DThird order

Q5 · Chemistry · Chemical Kinetics

The reaction NO₂(g) + CO(g) → NO(g) + CO₂(g) is believed to occur by the mechanism: Step 1 (slow): 2NO₂ → NO₃ + NO; Step 2 (fast): NO₃ + CO → NO₂ + CO₂. At constant temperature, [NO₂] is doubled and [CO] is tripled. By what factor does the rate change?

• A4
• B6
• C12
• D2

Q6 · Chemistry · Chemical Kinetics

The initial rates of the reaction A + B → products were measured at constant temperature in three experiments. Experiment 1: [A] = 0.04 M, [B] = 0.10 M, rate = 1.5 × 10⁻³ mol L⁻¹ s⁻¹. Experiment 2: [A] = 0.16 M, [B] = 0.10 M, rate = 1.2 × 10⁻² mol L⁻¹ s⁻¹. Experiment 3: [A] = 0.04 M, [B] = 0.30 M, rate = 4.5 × 10⁻³ mol L⁻¹ s⁻¹. What is the initial rate (in mol L⁻¹ s⁻¹) when [A] = 0.01 M and [B] = 0.20 M?

• A3.75 × 10⁻⁴
• B7.5 × 10⁻⁴
• C1.875 × 10⁻⁴
• D1.5 × 10⁻³

Q7 · Chemistry · Chemical Kinetics

A first-order reaction has a rate constant of 1.5 × 10⁻² s⁻¹. What is its rate constant expressed in min⁻¹?

• A0.9 min⁻¹
• B0.25 min⁻¹
• C1.5 min⁻¹
• D54 min⁻¹

Q8 · Chemistry · Chemical Kinetics

For a reaction X + Y → Z at constant temperature, three initial-rate experiments gave: (1) [X] = 0.10 M, [Y] = 0.10 M, rate = 4.0 × 10⁻⁴ mol L⁻¹ s⁻¹; (2) [X] = 0.20 M, [Y] = 0.10 M, rate = 1.6 × 10⁻³ mol L⁻¹ s⁻¹; (3) [X] = 0.20 M, [Y] = 0.30 M, rate = 4.8 × 10⁻³ mol L⁻¹ s⁻¹. What is the initial rate, in mol L⁻¹ s⁻¹, when [X] = 0.30 M and [Y] = 0.20 M?

• A7.2 × 10⁻³
• B3.6 × 10⁻³
• C2.4 × 10⁻³
• D1.44 × 10⁻²

Q9 · Chemistry · Chemical Kinetics

A first-order reaction has a half-life of 6.93 min. What is the rate of the reaction at the instant when the concentration of the reactant is 0.5 mol L⁻¹? (ln 2 = 0.693)

• A0.05 mol L⁻¹ min⁻¹
• B0.1 mol L⁻¹ min⁻¹
• C3.465 mol L⁻¹ min⁻¹
• D0.072 mol L⁻¹ min⁻¹

Q10 · Chemistry · Chemical Kinetics

For a reaction whose activation energy is zero, how does the rate constant k change when the temperature is increased?

• AIt remains constant, because e^(−Ea/RT) = 1 and k = A.
• BIt doubles for every 10 K rise in temperature.
• CIt increases linearly with absolute temperature.
• DIt decreases, because higher temperature always lowers the fraction of effective collisions.