Method of initial rates

Definition

The method of initial rates is a technique used to determine the rate law of a chemical reaction by measuring the initial rate of reaction for different starting concentrations of reactants. This method allows for the determination of the order of reaction with respect to each reactant.

5 Must Know Facts For Your Next Test

1. The initial rate is measured at the very beginning of the reaction where changes in concentration are minimal.
2. Plotting the initial rates against varying concentrations helps determine the order of reaction for each reactant.
3. The overall rate law can be expressed as $rate = k[A]^m[B]^n$ where $m$ and $n$ are determined experimentally.
4. Experiments must be designed carefully to isolate and vary one reactant concentration at a time while keeping others constant.
5. The method assumes that the reverse reaction is negligible at the initial stages.

Review Questions

• What information is needed to apply the method of initial rates?
• How can you determine the order of a reaction using this method?
• Why is it important to measure rates at early times in the method of initial rates?

Related terms

Rate Law:

An equation that relates the rate of a chemical reaction to the concentration of its reactants, typically in the form $rate = k[A]^m[B]^n$.

Reaction Order:

The power to which the concentration of a reactant is raised in a rate law, indicating how changes in concentration affect reaction rate.

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