CHEMICAL KINETICS WORKSHEET 1 WITH ANSWERS

 

Here are 20 multiple-choice questions (MCQs) from the chapter "Chemical Kinetics" for Class 12 board exam practice:

MCQs

1. The rate of a reaction is defined as: a) The change in concentration of reactants per unit time
   b) The change in concentration of products per unit time
   c) The sum of the change in concentration of reactants and products per unit time
   d) Both a and b

2. Which of the following factors does not affect the rate of a chemical reaction? a) Concentration of reactants
   b) Temperature
   c) Presence of a catalyst
   d) Color of the reactants

3. For a zero-order reaction, the rate is: a) Directly proportional to the concentration of the reactants
   b) Independent of the concentration of the reactants
   c) Inversely proportional to the concentration of the reactants
   d) Proportional to the square of the concentration of the reactants

4. The unit of rate constant for a first-order reaction is: a) mol L⁻¹ s⁻¹
   b) s⁻¹
   c) L mol⁻¹ s⁻¹
   d) mol² L⁻² s⁻¹

5. The half-life period of a first-order reaction is: a) Directly proportional to the initial concentration
   b) Inversely proportional to the initial concentration
   c) Independent of the initial concentration
   d) Proportional to the square of the initial concentration

6. For a chemical reaction, the activation energy is: a) The energy required to form the products
   b) The minimum energy required for the reactants to collide and react
   c) The total energy change during the reaction
   d) The difference in energy between the products and reactants

7. In the Arrhenius equation $k = A e^{\frac{-E_a}{RT}}$, $E_a$ represents: a) Rate constant
   b) Frequency factor
   c) Activation energy
   d) Energy of reaction

8. The overall order of a reaction with rate law $R = k[A]^2[B]$ is: a) 1
   b) 2
   c) 3
   d) 4

9. The slowest step in a reaction mechanism is called: a) Rate-determining step
   b) Fast step
   c) Activation step
   d) Catalyst step

10. Which of the following statements is correct for a catalyst? a) It increases the activation energy of a reaction
    b) It decreases the activation energy of a reaction
    c) It alters the equilibrium constant
    d) It is consumed during the reaction

11. For a reaction, if the rate constant doubles when the temperature is increased from 300 K to 310 K, the activation energy is approximately: a) 50 kJ/mol
    b) 100 kJ/mol
    c) 10 kJ/mol
    d) 200 kJ/mol

12. The rate law for a reaction is given by $R = k[A][B]^2$. The order of the reaction with respect to A and B are: a) 1 and 2, respectively
    b) 2 and 1, respectively
    c) 2 and 2, respectively
    d) 1 and 1, respectively

13. Which of the following reactions is an example of a first-order reaction? a) Radioactive decay
    b) Decomposition of ammonia
    c) Formation of water
    d) Combustion of methane

14. The rate of a reaction depends on: a) Only the concentration of reactants
    b) Concentration of reactants, temperature, and catalyst
    c) Only the temperature
    d) Only the concentration of products

15. For a reaction, the rate constant $k$ is given as $k = 2.5 \times 10^{-2}$ s⁻¹. The reaction follows: a) Zero-order kinetics
    b) First-order kinetics
    c) Second-order kinetics
    d) Third-order kinetics

16. In an elementary reaction, the molecularity is: a) The same as the order of the reaction
    b) Always greater than the order of the reaction
    c) Equal to the sum of the stoichiometric coefficients of reactants
    d) The number of molecules colliding simultaneously

17. For a second-order reaction, the plot of $\frac{1}{[A]}$ vs. time is: a) Linear with a negative slope
    b) Linear with a positive slope
    c) Parabolic
    d) Exponential

18. The rate of decomposition of hydrogen peroxide increases in the presence of manganese dioxide because: a) Manganese dioxide acts as a reactant
    b) Manganese dioxide acts as a product
    c) Manganese dioxide acts as a catalyst
    d) Manganese dioxide raises the activation energy

19. The rate constant for a reaction increases by a factor of 4 when the temperature increases from 300 K to 350 K. The reaction is likely to have: a) Low activation energy
    b) High activation energy
    c) No activation energy
    d) Zero activation energy

20. The reaction $2N_2O_5 \to 4NO_2 + O_2$ is an example of a: a) First-order reaction
    b) Second-order reaction
    c) Zero-order reaction
    d) Third-order reaction

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Answers

1. (d) Both a and b
2. (d) Color of the reactants
3. (b) Independent of the concentration of the reactants
4. (b) s⁻¹
5. (c) Independent of the initial concentration
6. (b) The minimum energy required for the reactants to collide and react
7. (c) Activation energy
8. (c) 3
9. (a) Rate-determining step
10. (b) It decreases the activation energy of a reaction
11. (a) 50 kJ/mol
12. (a) 1 and 2, respectively
13. (a) Radioactive decay
14. (b) Concentration of reactants, temperature, and catalyst
15. (b) First-order kinetics
16. (d) The number of molecules colliding simultaneously
17. (b) Linear with a positive slope
18. (c) Manganese dioxide acts as a catalyst
19. (b) High activation energy
20. (a) First-order reaction

These questions will help in understanding key concepts from the chapter on "Chemical Kinetics."