Chemical Kinetics — Class 12 Chemistry PYQs

For the reaction X + 2Y → P, the differential form equation of the rate law is :

(A) $2\frac{d[\text{P}]}{dt}=-\frac{d[\text{Y}]}{dt}$

(B) $-\frac{d[\text{P}]}{dt}=-\frac{d[\text{X}]}{dt}$

(C) $+\frac{d[\text{X}]}{dt}=-\frac{d[\text{P}]}{dt}$

(D) $-2\frac{d[\text{Y}]}{dt}=+\frac{d[\text{P}]}{dt}$

A zero-order reaction is one whose rate is independent of :
(A) Presence of light
(B) Concentration of the reactant
(C) Temperature of the reaction
(D) Pressure of the reaction

A reaction A₂ + B₂ → 2AB occurs by the following mechanism :

A₂ → A + A   (slow)

A + B₂ → AB + B   (fast)

A + B → AB   (fast)

Its order would be :
(A) 1
(B) 2
(C) Zero
(D) 1/2

In the Arrhenius equation, when log k is plotted against 1/T, a straight line is obtained whose :
(A) slope is A/R and intercept is Ea.
(B) slope is A and intercept is -Ea/R.
(C) slope is -Ea/RT and intercept is log A.
(D) slope is -Ea/2.303 R and intercept is log A.

Half-life period of a first order reaction is 1386 seconds. The rate constant (k) of the reaction is :
(A) 0.5 × 10⁻³ s⁻¹
(B) 5.0 × 10⁻³ s⁻¹
(C) 5 × 10⁻² s⁻¹
(D) 0.5 × 10⁻² s⁻¹

For a certain reaction R → products, a plot of log [R] vs. time gives a straight line with a slope of – 1.25 s⁻¹. The order of the reaction is :
(A) One
(B) Zero
(C) Two
(D) Fractional

For a zero order reaction A → products, t1/2 is :
(A) [A]0 / k
(B) 2.303 log 2 / k
(C) 1 / k[A]0
(D) [A]0 / 2k
where [A]0 = initial concentration of the reactant, k = rate constant.

The addition of catalyst during a chemical reaction alters which of the following quantities of the reaction ?
(A) Enthalpy
(B) Activation energy
(C) Entropy
(D) Internal energy

For the elementary reaction P→Q, the rate of disappearance of ‘P’ increases by a factor of 8 upon doubling the concentration of ‘P’. The order of the reaction with respect to ‘P’ is :
(A) 3
(B) 4
(C) 2
(D) 1

The rate of the reaction 2A + B₂ → 2AB is given by Rate = k [A]2 [B₂]. The value of rate constant (k) can be increased by :
(A) increasing the concentration of A
(B) increasing the concentration of B
(C) increasing the temperature
(D) all the above three