6.5 Reaction Mechanisms

Question 1

What does a reaction mechanism show?

Answer 1

All the simple steps that make up a more complex reaction.

Question 2

What is the rate determining step?

Answer 2

The slowest step with the highest activation energy in a reaction mechanism.

Question 3

What is molecularity?

Answer 3

The number of reactant particles taking part in a particular step usually the RDS in a reaction mechanism.

Question 4

How can you evaluate a reaction mechanism?

Answer 4

Each step must involve a maximum of two particles colliding - it is statically highly unlikely that more than two particles would ever come together at exactly the same time.
The mechanism must agree the stoichiometric equation - when all the individual nations are added together cancelling out like terms you must end up with the overall chemical equations.
The rate equation contains concentration of reactants involved in the mechanism up to and including the rate determining step.
The order of a reactant in the rate equation indicates the number of times the reactant appears in the mechanism up to and including the rate determining step.

Question 5

How are catalysts involved in reaction mechanisms?

Answer 5

A catalyst is involved in the rate determining step
Introduces a step with lower activation energy
Allows the reaction to occur by a different mechanism.