Topic 6 - Chemical Kinetics

Question 1

Activation energy

Answer 1

The minimum amount of energy required for a reaction to occur between two particles.

The other requirement is that the particles have to have an appropriate geometry of collision.

Question 2

Catalyst

Answer 2

Provide an alternative pathway for a reaction so that the activation energy required to reach the activation complex is lowered.

2 types:
Homogenous catalysts = same phase as the reactants

Heterogeneous catalysts = different phase as the reactants
(Bring the reactant particles into close alignment by adsorbing them onto the catalytic surface.)

Question 3

Half-life

Answer 3

The time taken for the concentration of the reactant to fall to half of its initial value.

Question 4

Order of reaction

Answer 4

The rate is always proportional to the concentration of a reactant raised to a power, where the power is the order of the reaction with respect to that reactant.

Question 5

Rate expression

Answer 5

An equation that shows the relationship between the concentrations of the reactants and the rate of the reaction.

Every species in the rate expression must occur in the rate determining step or in an equilibrium occurring before it.

Question 6

Rate of reaction

Answer 6

The rate of increase of concentration of one of the products.
The rate of decrease of concentration of one of the reactants.

Question 7

Rate-determining step

Answer 7

The slowest step of a reaction / with the lowest activation energy.
This determines the rate of the entire reaction.