CBSE Class 12 Chemistry Chemical Kinetics MCQs Set 04

Question. If the rate of the reaction is equal to the rate constant, the order of the reaction is
(a) 0
(b) 1
(c) 2
(d) 3

Answer : A

Question. 2A B → C, It would be a zero order reaction when
(a) the rate of reaction is proportional to square of concentration of A
(b) the rate of reaction remains same at any concentration of A
(c) the rate remains unchanged at any concentration of B and C
(d) the rate of reaction doubles if concentration of B is increased to double.

Answer : B

Question. For the reaction; 2N₂O₅ → 4NO₂ + O₂ rate and rate constant are 1.02 × 10^–4 and 3.4 × 10^–5 sec^–1 respectively, then concentration of N₂O₅ at that time will be
(a) 1.732
(b) 3
(c) 1.02 × 10^–4
(d) 3.4 × 10₅

Answer : B

Question. The half-life of a substance in a certain enzymecatalysed reaction is 138 s. The time required for the concentration of the substance to fall from 1.28 mg L^–1 to 0.04 mg L^–1 is
(a) 414 s
(b) 552 s
(c) 690 s
(d) 276 s

Answer : C

Question. Half-life period of a first order reaction is 1386 seconds. The specific rate constant of the reaction is
(a) 0.5 × 10^–2 s^–1
(b) 0.5 × 10^–3 s^–1
(c) 5.0 × 10^–2 s^–1
(d) 5.0 × 10^–3 s^–1

Answer : B

Question. If 60% of a first order reaction was completed in 60 minutes, 50% of the same reaction would be completed in approximately (log 4 = 0.60,log 5 = 0.69)
(a) 45 minutes
(b) 60 minutes
(c) 40 minutes
(d) 50 minutes.

Answer : A

Question. N₂ (g) + 2H₂ (g) ⇌ 2NH₃ (g) + 22 kcal
The activation energy for the forward reaction is 50 kcal. What is the activation energy for the backward reaction?
(a) 72 kcal
(c) -72 kcal
(b) 28 kcal
(d) -28kcal

Answer : A

Question. A given sample of milk turns sour at room temperature (27°C) in 5 h. In a refrigerator at -3° C., it can be stored 10 times longer. The energy of activation for the souring of milk is
(a) 2.303 x 5 R kJ mol^-1
(b) 2.303 x 3 R kJ mol^-1
(c) 2.303 x 2.7 R kJ mol^-1
(d) 2.303 x 10 R kl mol^-1

Answer : C

Question. The rate of a chemical reaction doubles for every 10°C rise of temperature. If the temperature is raised by 50°C., the rate of the reaction increases by about
(a) IO times
(b) 24 times
(c) 32 times
(d) 64 times

Answer : C

Question. In a zero-order reaction, for every 10 °C rise of temperature, the rate is doubled. If the temperature is increased from 10 °C to 100 °C, the rate of the reaction will become
(a) 256 times
(b) 512 times
(c) 64 times
(d) 128 times.

Answer : B

Question. The rate of the reaction, 2NO + Cl₂ → 2NOCl is given by the rate equation, rate = k[NO]₂[Cl₂]. The value of the rate constant can be increased by
(a) increasing the temperature
(b) increasing the concentration of NO
(c) increasing the concentration of the Cl₂
(d) doing all of these.

Answer : A

Question. The activation energy for a simple chemical reaction A ⇌ B is Ea in forward direction. The activation energy for reverse reaction
(a) is negative of Ea
(b) is always less than Ea
(c) can be less than or more than Ea
(d) is always double of Ea.

Answer : C

Question. In a reaction, A + B → product, rate is doubled when the concentration of B is doubled, and rate increases by a factor of 8 when the concentration of both the reactants (A and B) are doubled, rate law for the reaction can be written as
(a) rate = k[A][B]²
(b) rate = k[A]²[B]²
(c) rate = k[A][B]
(d) rate = k[A]²[B]

Answer : D

Question. Which one of the following statements for the order of a reaction is incorrect?
(a) Order can be determined only experimentally.
(b) Order is not influenced by stoichiometric coefficient of the reactants.
(c) Order of a reaction is sum of power to the concentration terms of reactants to express the rate of reaction.
(d) Order of reaction is always whole number.

Answer : D

Question. The unit of rate constant for a zero order reaction is
(a) mol L^–1 s^–1
(b) L mol^–1 s^–1
(c) L2 mol^–2 s^–1
(d) s^–1

Answer : A

Question. The rate of a first order reaction is 1.5 × 10^–2 mol L^–1 min^–1 at 0.5 M concentration of the reactant. The half-life of the reaction is
(a) 0.383 min
(b) 23.1 min
(c) 8.73 min
(d) 7.53 min

Answer : B

Question. The reaction A B follows first order kinetics. The time taken for 0.8 mole of A to produce 0.6 mole of B is 1 hour. What is the time taken for conversion of 0.9 mole of A to produce 0.675 mole of B ?
(a) 1 hour
(b) 0.5 hour
(c) 0.25 hour
(d) 2 hours

Answer : A

Question. For a reaction taking place in three steps, the rate constants are k₁ , k₂ and k₃ and overall rate constant is k = k₁k₃ / k₂ . If the energies of activation E₁, E₂ and E₃ are 60, 30 and 10 kJ mol^-1 , respectively, then the overall energy of activation is
(a) 30 kJ mol^-1
(b) 40 kJ mol^-1
(c) 60 kJ mol^-1
(d) l00 kJ mol^-1

Answer : B

Question. What is the activation energy for a reaction if its rate doubles when the temperature is raised from 20 °C to 35 °C? (R = 8.314 J mol^–1 K^–1)
(a) 34.7 kJ mol^–1
(b) 15.1 kJ mol^–1
(c) 342 kJ mol^–1
(d) 269 kJ mol^–1

Answer : A

Question. When a biochemical reaction is carried out in laboratory, outside the human body in absence of enzyme, then rate of reaction obtained is 10–6 times, the activation energy of reaction in the presence of enzyme is
(a) 6/RT
(b) P is required
(c) different from Ea obtained in laboratory
(d) can’t say anything.

Answer : C

Question. How enzymes increases the rate of reactions?
(a) By lowering activation energy
(b) By increasing activation energy
(c) By changing equilibrium constant
(d) By forming enzyme substrate complex

Answer : A

Question. A chemical reaction was carried out at 300 K and 280 K. The rate constants were found to be k₁ and k₂ respectively. Then
(a) k₂ ≈ 0.25 k₁
(b) k₂ ≈0.5 k₁
(c) k₂ ≈ 4 k₁
(d) k₂ ≈ 2 k₁

Answer : A

Question. The rate of a reaction is doubled for every 10° rise in temperature. The increase in reaction rate as a result of temperature rise from 10° to 100° is
(a) 112
(b) 512
(c) 400
(d) 614
(e) 100

Answer : B

Question. The activation energy of a reaction at a given temperature is found to be 2.303 RT J mol^-1. The ratio of rate constant to the Arrhenius factor is
(a) 0.01
(b) 0.1
(c) 0.02
(d) 0.001

Answer : B

Question. The rate ofreaction doubles when its temperature changes from 300 K to 310 K. Activation energy of such a reaction will be(R = 8.314 JK^-1 mol^-1 and log 2 = 0.301)
(a) 53.6 kJ mol^-1
(b) 48.6 kJ mol^-1
(c) 58.5 kJ mol^-1
(d) 60.5 kJ mol^-1

Answer : A

Question. For a reaction, activation energy Ea = 0 and the rate constant at 200 K is 1.6 × 106 s^–1. The rate constant at 400 K will be [Given that gas constant R = 8.314 J K^–1 mol^–1]
(a) 3.2 × 104 s^–1
(b) 1.6 × 106 s^–1
(c) 1.6 × 103 s^–1
(d) 3.2 × 106 s^–1

Answer : B

Question. The addition of a catalyst during a chemical reaction alters which of the following quantities?
(a) Enthalpy
(b) Activation energy
(c) Entropy
(d) Internal energy

Answer : B