Kinetics exam QS

Question 1

The diagram below shows the Maxwell–Boltzmann distribution of molecular energies
in a sample of a gas.

Explain the process that causes some molecules in this sample to have very
low energies

Answer 1

Collisions (1)
Cause some molecules to slow down or lose energy (1)

Question 2

Explain why, even in a fast reaction, a very small percentage of collisions
leads to a reaction.

Answer 2

Only a small percentage/very few collisions have E >Ea

Question 3

What is the effect of an increase in temperature on the rate of a chemical
reaction?
Explain your answer with reference to the Maxwell–Boltzmann distribution.

Answer 3

(Rate of reaction) increases

(At a higher temperature) more molecules/particles

have the minimum energy needed to react/have activation
energy/have successful collisions

Question 4

What is the effect of the addition of a catalyst on the rate of a chemical
reaction?
Explain your answer with reference to the Maxwell–Boltzmann distribution.

Answer 4

(Rate of reaction) increases
lowers activation energy
so that more molecules are able to react

Question 5

Explain how a catalyst increases the rate of a reaction.

Answer 5

Catalysts provide an alternative route/pathway/mechanism that has a lower activation energy

Question 6

Give the meaning of the term activation energy

Answer 6

• the minimum energy for a reaction to occur

Question 7

For each of the following reactions, identify a catalyst and name the organic product
of the reaction.
(i) The fermentation of an aqueous solution of glucose.
Catalyst

Name of organic product .

Answer 7

yeast as catalyst

ethanol is organic product

Question 8

Explain why a small increase in temperature has a large effect on the initial rate of a
reaction.

Answer 8

Small increase in temperature results in many more molecules having energy greater than the activation energy
( compared to increasing conc)