Rate-limiting step

Definition

The rate-limiting step is the slowest step in a reaction mechanism that determines the overall reaction rate. It acts as a bottleneck, limiting the speed at which products are formed.

5 Must Know Facts For Your Next Test

1. The rate-limiting step has the highest activation energy compared to other steps in the mechanism.
2. It dictates the overall reaction rate and is used to derive the rate law for complex reactions.
3. Identifying the rate-limiting step often involves analyzing intermediates and transition states.
4. Catalysts can alter the rate-limiting step by providing an alternative pathway with lower activation energy.
5. In multi-step mechanisms, only the reactants involved in the rate-limiting step appear in the rate law.

Review Questions

• What characteristic of a reaction mechanism makes it responsible for determining the overall reaction rate?
• How does a catalyst affect the rate-limiting step of a chemical reaction?
• Why do only certain reactants appear in the rate law for reactions with multiple steps?

Related terms

Activation Energy:

The minimum energy required for a chemical reaction to occur.

Transition State:

A high-energy state during a chemical reaction where old bonds break and new bonds form.

Catalyst:

A substance that increases the reaction rate by lowering the activation energy without being consumed in the process.