# Worksheet on Chemical Kinetics

Chemical Kinetics deals with the study of chemical reaction with respect to reaction rates, effect of various variables, re-arrangement of atoms, formation of intermediates etc.

In simple words chemical kinetics is also known as reaction Kinetics.

Here you can find some question related to “Chemical Kinetics” and their answers:

Questions:

1. The one which is a unimolecular reaction is:

(a)    $H_2 + Cl_2 \to 2HCl$

(b)   $N_2O_5 \to N_2O_4 + \dfrac{1}{2}O_2$

(c)    $PCl_3 + Cl_2 \to PCl_5$

(d)   $2HI \to H_2 + I_2$

2. Which of the following rate laws expresses total order 0.5?

(a)    $\text{Rate} = k(C_x)^{0.5} (C_y)^{0.5} (C_z)^{0.5}$

(b)   $\text{Rate} = k(C_x)^{0.5} (C_z)^0 /(C_y)^2$

(c)    $\text{Rate} = k(C_x)^{1.5} (C_y)^{-1} (C_z)^0$

(d)   $\text{Rate} = k(C_x)(C_y) (C_z)$

3. Which of the following reactions will be a pseudo first order reaction?

(a)    $H_2O_2 \to H_2O + \dfrac{1}{2}O_2$

(b)   $N_2O_5 \to N_2O + \dfrac{1}{2}O$

(c)    $H_2 + I_2 \to 2HI$

(d)   None of these

4. The equation which expresses the effect of temperature on the velocity constant of a reaction is:

(b)   Arrhenius

(d)   None of these

5. According to the collision theory the rate of a reaction depends on:

(a)    The total number of molecules

(b)   The average velocity of molecules

(c)    The number of colliding molecules per ml. per unit time

(d)   None of these ( )

6. The log K for a reaction is plotted against 1/ T. The slope of a straight line will give:

(a)    Number of collisions

(b)   Frequency factor

(c)    Energy of activation

(d)   None of these

7. The dimensions of rate constant of a second order reaction involves:

(a)    Only time

(b)   Time and square of concentration

(c)    Time and concentration

(d)   Neither time nor concentration

8. The rate of a reaction between A and B increases by a factor of 100, when the concentration of A is increased 10 folds. The order of the reaction with respect to A is:

(a)    3

(b)   2

(c)    4

(d)   10

9. For the chemical reaction A B it is found that the rate of the reaction doubles when the concentration of A is increased four times. The order with respect to ‘A’ for this reaction is:

(a)    5

(b)   1/2

(c)    0

(d)   1/4

10. For the reaction,

$H_2 + Br_2 \to 2HBr$ if the rate law is,

$\dfrac{dx}{dt} = k[H_2][Br_2]^{1/2}$ then what  is true for this reaction?

(a)    Mole cularity for this reaction is 3/ 2

(b)   The unit for k is per second

(c)    The reaction is of second order

(d)    The molecularity of this reaction is 2

11. The rate of reaction is calculated from the:

(a)    Slope of a graph

(b)   Tangent of a graph

(c)    Intercept of a graph

(d)   Equation of a parabola

12. For a first-order the rate of reaction is $1.0 \times 10^{-2}Mol^{-1} S^{-1}$ and the initial concentration of the reactant is 1 M. The half-life period for the reaction is:

(a)    $0.0693 S^{-1}$

(b)   $6.93 \times 10^{-3} S^{-1}$

(c)    $0.693 S^{-1}$

(d)   $6.93 \times 10^{-3} S^{-1}$

13. Which of the following statements is not true for a zero-order reaction?

(a)    The rate constant has the unit mol $L^{-1}1 S^{-1}$

(b)    The rate is independent of the concentrations of the reactants

(c)    The rate is independent of the temperature of the reaction

(d)   The half-life of the reaction depends on the concentrations of the reactants

14. If $E_a$ of a reaction is zero, k is equal to:

(a)    Zero

(b)   A

(c)    $A^{-1}$

(d)   Infinity

15. 75% of a first-order reaction was completed in 30 minutes. How long did it take to complete of 50 % of the reaction?

(a)    64 min

(b)   24 min

(c)    15 min

(d)   8 min

16. Trimolecular reactions are uncommon because:

(a)    The probability of three molecules colliding at an instant is high

(b)   The probability of many molecules colliding at an instant is high

(c)    The probability of three molecules colliding at at instant is almost zero

(d)   The probability of three molecules colliding at an instant is low

17. In a reaction, the threshold energy is equal to:

(a)    Activation energy – normal energy of the reactants

(b)   Activation energy + entropy of the reactants

(c)    Activation energy + normal energy of the reactants

(d)   Activation energy

18. The activation energy of a reaction may be decreased by:

(a)    Decreasing the enthalpy

(b)   Increasing the volume of the reactants

(d)   Decreasing the entropy

19. The rate constant is given by the equation $k = p z. c^{-E/RT}$. Which of the factors should register a decrease for the reaction to proceed more rapidly?

(a)    E

(b)   T

(c)    Z

(d)   P

20. Which of the following statement about the order of a reaction is true:

(a)    The order of reaction can be determined from the balanced equation

(b)   A second-order reaction is also bimolecular

(c)    The order of a reaction increases with increase in temperature

(d)   The order of a reaction can only be determined by experiment

21. The rate of the  reaction is $A + B + C \to \text{Products}$ is given by: $\text{rate} K[A]^{1/2}[B]^{1/3}[C]^{1/4}$

The order the reaction is:

(a)    2

(b)   1/2

(c)    2

(d)   13/12

22. An endothermic reaction $A \to B$ has an activation energy of reaction is 5 kcal/mole. The activation energy of the reaction $B \to A$ is:

(a)    15 kcal/mole

(b)   10 kcal/mole

(c)    20 kcal/ mole

(d)   Zero

23.  A first order reaction has a rate constant of $1.15 \times S^{-1}$. How long will 5 g. of this reactant take to reduce to 3 g?

(a)    111 sec

(b)   555 sec

(c)    444 sec

(d)   222 sec

24.  In a zero order reaction 1 / 3 of the reactant is consumed in one hour. The percentage amount of the reactant that will be left behind at the end of 3 hours is:

(a)    11.11

(b)   33.33

(c)    2.66

(d)   zero

25.  A specific reaction rate 6.68 mol $litre^{-1} sec^{-1}$ refers to:

(a)    Zero order reaction

(b)   Second order reaction

(c)    Reaction of third order

(d)   First order reaction

1.(b)          2. (c)        3. (d)        4. (b)             5. (c)

6. (c)        7. (c)        8. (b)         9. (b)             10. (d)

11. (a)      12. (d)      13. (c)        14. (b)           15. (c)

16. (c)      17. (c)      18. (c)        19. (d)          20. (d)

21. (b)     22. (b)      23. (c)        24. (d)          25. (a)

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