Reaction orders

Definition

Reaction orders indicate the power to which the concentration of a reactant is raised in the rate law expression. They help determine how changes in concentration affect the reaction rate.

5 Must Know Facts For Your Next Test

1. The overall reaction order is the sum of the exponents of all reactants in the rate law.
2. Reaction orders can be zero, fractional, or whole numbers.
3. Determining reaction order requires experimental data and cannot be deduced from the balanced equation alone.
4. A zero-order reaction means that the rate is independent of the concentration of that reactant.
5. First-order reactions have a linear relationship between rate and concentration, while second-order reactions depend on the square of concentration.

Review Questions

• What does it mean for a reaction to be zero-order with respect to a particular reactant?
• How do you determine the overall order of a reaction from its rate law?
• Why can't reaction orders be determined directly from a balanced chemical equation?

Related terms

Rate Law: An equation that relates the reaction rate to the concentrations of reactants, often including a rate constant.

Rate Constant (k): A proportionality constant in the rate law that is specific to a particular reaction at a given temperature.

Integrated Rate Law: An expression that shows how reactant concentrations change over time, derived by integrating the basic rate laws.