# MCQ Questions for Class 12 Chemistry Chapter 4 Chemical Kinetics with Answers

Students may want to download NCERT MCQ Questions for Class 12 Chemistry Chapter 4 Chemical Kinetics with Answers Pdf free download. This Chemical Kinetics Class 12 MCQs Questions with Answers can help understand the concepts score better in your Class 12 Chemistry Exam, so make sure you practice these! Check out chapter-wise MCQ Questions for Class 12 Chemistry with Answers.

## Chemical Kinetics Class 12 MCQs Questions with Answers

Solve this Chemical Kinetics Multiple Choice Questions of Class 12 Chemistry Chapter 4 MCQ, so as not to miss out on any concept from being clear about what they mean!

Question 1.
A first order reaction has a half life period of 34.65 seconds. Its rate constant is
(a) 2 × 10-2 s-1
(b) 4 × 10-4 s-1
(c) 20 s-1
(d) 2 × 10-4 s-1

Answer: (a) 2 × 10-2 s-1

Question 2.
If a graph is plotted between In k and 1/T for the first order reaction, the slope of the straight line so obtained is given by
(a) –$$\frac { E_a }{R}$$
(b) $$\frac { E_a }{2.303 R}$$
(c) $$\frac { 2.303 }{E_a.R}$$
(d) $$\frac { E_a }{2.303}$$

Answer: (a) –$$\frac { E_a }{R}$$

Question 3.
The unit of rate constant for a zero order reaction is
(a) mol L-1s-1
(b) s-1
(c) L mol-1s-1
(d) L2mol-2s-1

Question 4.
A catalyst increases the speed of a chemical reaction by
(a) increasing activation energy
(b) decreasing activation energy
(c) increasing reactant energy
(d) decreasing threshold energy

Question 5.
The units of the rate constant for the second order reaction are:
(a) mol-1 litre s-1
(b) mol litre-2 s-1
(c) s-1
(d) mol litre-1 s-1

Question 6.
The value of k for a reaction is 2.96 × 10-30 s-1. What is the order of the reaction?
(a) Zero
(b) 3
(c) 2
(d) 1

Question 7.
A reaction is found to be of second order with respect to concentration of carbon monoxide. If concentration of carbon monoxide is doubled, the rate of reaction will
(a) triple
(b) increase by a factor of 4
(c) double
(d) remain unchanged

Answer: (b) increase by a factor of 4

Question 8.
If the concentrations are expressed in mol litre-1 and time in s, then the units of rate constant for the first-order reactions are
(a) mol litre-1 s-1
(b) mol-1 litre s-1
(c) s-1
(d) mol² litre-2 s-1

Question 9.
The half life of a first order reaction having rate constant 200 s-1 is
(a) 3.465 × 10-2 s
(b) 3.465 × 10-3 s
(c) 1.150 × 10-2 S
(d) 1.150 × 10-3 S

Answer: (b) 3.465 × 10-3 s

Question 10.
The rate of a reaction is 1.209 × 10-4L² mol-2s-1. The order of the reaction is:
(a) zero
(b) first
(c) second
(d) third

Question 11.
A catalyst increases the rate of a reaction by
(a) increasing threshold energy
(b) increasing activation energy
(c) activating the reactants
(d) lowering activation energy

Question 12.
Time required for 100% completion of a zero order reaction is:
(a) t100% = a/k
(b) t100% = a.k
(c) t100% = a/2k
(d) None of these

Question 13.
Arrhenius equation is represented by:
(a) k = AeEa/RT
(b) k = Ae-Ea/RT
(c) t1/2 = 0.693/k
(d) None of these

Question 14.
The overall order of a reaction, which has the rate expression: Rate = AC[A]1/2[B]3/2 is:
(a) First order
(b) Second order
(c) Third order
(d) Zero order

Question 15.
If half life period of a first order reaction is 100 seconds. Then rate constant will be:
(a) 6.93 × 10-3 second-1
(b) 6.93 × 10-2 second-1
(c) 0.693 second-1
(d) 6.93 second-1

Answer: (a) 6.93 × 10-3 second-1

Question 16.
If rate constant for a reaction is mole litre-1 second-1, then order of reaction is:
(a) Zero order
(b) First order
(c) Second order
(d) None of these

Question 17.
Identify the order of reaction from the given rate constant k = 2.6 × 10-4 L mol-1 s-1
(a) First
(b) Zero
(c) Second
(d) None of these

Question 18.
For a reaction: N2 + 3H2 → 2NH3, the rate of reaction with respect to NH3 will be:
(a) –$$\frac{d\left[\mathrm{NH}_{3}\right]}{d t}$$
(b) –$$\frac{d[NH_3]^2}{d t}$$
(c) +$$\frac { 1 }{10}$$ $$\frac { d[NH_3] }{dt}$$
(d) –$$\frac { 1 }{10}$$ $$\frac { d[NH_3] }{dt}$$

Answer: (c) +$$\frac { 1 }{10}$$ $$\frac { d[NH_3] }{dt}$$

Question 19.
Half life period of a first order reaction depends upon:
(a) Concentration of reactants
(b) Concentration of products
(c) Rate constant of reaction
(d) None of these

Answer: (c) Rate constant of reaction

Question 20.
Half life period of a first order reaction is:
(a) directly proportional to the initial concentration of the reactant
(b) half of the rate constant
(c) same for all reactions
(d) independent of the initial concentration of the reactants

Answer: (d) independent of the initial concentration of the reactants

Assertion and Reason Type Questions

The questions given below consist of an assertion and a reason. Use the following key to choose the appropriate answer.
(a) Both Assertion (A) and Reason (R) are correct statements, and Reason (R) is the correct explanation of the Assertion (A).
(b) Both Assertion (A) and Reason (R) are correct statements, but Reason (R) is not the correct explanation of the Assertion (A).
(c) Assertion (A) is correct, Reason (R) is wrong statement.
(d) Assertion (A) is wrong, but Reason (R) is correct statement.

Question 21.
Assertion: Rate of reaction increases with increase in temperature.
Reason: Number of collisions increases – with increase in temperature.

Answer: (a) Both Assertion (A) and Reason (R) are correct statements, and Reason (R) is the correct explanation of the Assertion (A).

Question 22.
Assertion: Reactions of higher order are rare.
Reason: The chances of simultaneous multimolecular collisions are extremely small.

Answer: (a) Both Assertion (A) and Reason (R) are correct statements, and Reason (R) is the correct explanation of the Assertion (A).

Question 23.
Assertion: The half life period for a first order reaction is independent of initial concentration of reactants.
Reason: For first order reaction, t1/2 = $$\frac { 0.693 }{k}$$

Answer: (a) Both Assertion (A) and Reason (R) are correct statements, and Reason (R) is the correct explanation of the Assertion (A).

Question 24.
Assertion: For the first order reaction the units of rate constant are time-1.
Reason: The rate of first order reaction remains constant throughout.

Answer: (c) Assertion (A) is correct, Reason (R) is wrong statement.

Question 25.
Assertion: For a first order reaction, graph of [A] vs. t is a straight line.
Reason: For first order reaction, k = $$\frac { 2.303 }{t}$$ log $$\frac { [R]_0 }{[R]}$$

Answer: (d) Assertion (A) is wrong, but Reason (R) is correct statement.

Question 26.
Assertion: For complex reactions molecularity and order are not same.
Reason: Order of a reaction may be zero.

Answer: (b) Both Assertion (A) and Reason (R) are correct statements, but Reason (R) is not the correct explanation of the Assertion (A).

Question 27.
Assertion: A catalyst increases the rate of a reaction.
Reason: A catalyst forms an activated complex of lower potential energy.

Answer: (a) Both Assertion (A) and Reason (R) are correct statements, and Reason (R) is the correct explanation of the Assertion (A).

Question 28.
Assertion: The molecularity of the reaction
H2 + Br2 → 2HBr is 2.
Reason: Order of the reaction is 3/2.

Answer: (c) Assertion (A) is correct, Reason (R) is wrong statement.

Question 29.
Assertion: For the reaction:
RCl + NaOH (aq) → ROH + NaCl, the rate of reaction is reduced to half when the concentration of RCl is reduced to half.
Reason: The rate of reactions is represented by k[RCl], i.e. it is a first order reaction.

Answer: (c) Assertion (A) is correct, Reason (R) is wrong statement.

Question 30.
Assertion: Photochemical reactions always occur in the presence of light.
Reason: Photochemical reactions even with, ΔG = +ve occur.