11) The collision frequency is directly proportional to the:

a) Absolute temperate.
b) Square root of the absolute temperature.
c) Square of absolute temperature.
d) None of these.

ANSWER : Square root of the absolute temperature.

12) The rate of a reaction doubles when the temperature changes from 27°C to 37°C. Calculate the energy of activation.

a) 54.6 kJ mol^-1
b) 53.6 kJ mol^-1
c) 52.6 kJ mol^-1
d) 54.1 kJ mol^-1

ANSWER : 53.6 kJ mol^-1

13) Which among the following is not an example of second order reaction?

a) Dissociation of HI.
b) Dissociation of COCl₂
c) Saponification of ethyl acetate.
d) Reaction between NO and O₃.

ANSWER : Dissociation of COCl₂

14) The unit of rate constant is:

a) Moles L^-1 time^-1
b) Time^-1
c) L mol^-1 time^-1
d) All of these.

ANSWER : All of these.

15) At room temperature, most of the reactant molecules have:

a) Energy less than the threshold value.
b) Energy more than the threshold value.
c) Energy same as the threshold value.
d) Energy, independent of the threshold value.

ANSWER : Energy less than the threshold value.

16) The rate constant of a reaction is 1.2 x 10^-3 sec^-1 at 30°C and 2.1 x 10^-3 sec^-1 at 40°C. Calculate the energy of activation of the reaction.

a) 67.32 kJ mol^-1
b) 98.76 kJ mol^-1
c) 44.13 kJ mol^-1
d) 12.45 kJ mol^-1

ANSWER : 44.13 kJ mol^-1

17) The value of rate constant at 313 K is 1.8 x 10^-5sec^-1. Calculate the frequency factor A (Ea = 94.14 kJ mol^-1)

a) 9.194 x 10¹⁰ collisions / sec

b) 45.146 x 10¹⁰ collisions / sec

c) 9.194 x 10⁸ collisions / sec

d) 45.146 x 10⁸ collisions / sec

ANSWER : 9.194 x 10¹⁰ collisions / sec

18) The role of catalyst in a chemical reaction is to change:

a) Equilibrium constant.
b) Activation energy.
c) Heat of reaction.
d) Products of reaction.

ANSWER : Activation energy.

19) The ionic reactions are very fast because:

a) These reactions are highly exothermic.
b) The energy of interaction between charged ions is greater than between neutral molecules.
c) It does not involve bond breaking.
d) The number of collisions between ions per unit volume per second is very large.

ANSWER : It does not involve bond breaking.

20) Which one of the following statement explains the fact that the reactions of high molecularity are rare?

a) Many body collisions have low probability.
b) The more the number of colliding particles, the more is the weight and hence difficult to cross the barrier.
c) Many body collisions are not energetically favoured.
d) The activation energy for many body collisions becomes very large.

ANSWER : Many body collisions have low probability.

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