5.1.4: Rate-determining step

Question 1

What is the rate-determining step?

Answer 1

The slowest step in the reaction mechanism of a multi-step reaction.

Question 2

What is a reaction mechanism?

Answer 2

A series of steps that, together, make up the overall reaction.

Question 3

What is an intermediate?

Answer 3

A species formed in one step of a multi-step reaction that is used up in subsequent steps, and is not seen as either a reactant or a product of the overall equation.

Question 4

When you measure the rate of any reaction that has a multi-step reaction, what are you effectively measuring?

Answer 4

The rate of the rate-determining step.

Question 5

How can you use rate equations to predict reaction mechanisms?

Answer 5

• Zero order reactants have no influence on the rate of reaction.
• They do not appear in the rate equation.
• If they have no influence on rate, they cannot be involved in the rate-determining step.
• Also, the order of a reactant in the rate equation tells us how many moles of it are involved in the rate determining step.