Rate constant

Definition

The rate constant, often denoted as $k$, is a proportionality factor in the rate equation that relates the reaction rate to the concentration of reactants. Its value is specific to a particular reaction and changes with temperature.

5 Must Know Facts For Your Next Test

1. The units of the rate constant vary depending on the overall order of the reaction.
2. For a first-order reaction, the unit of $k$ is $s^{-1}$.
3. The rate constant can be determined experimentally by measuring how the concentration of reactants or products changes over time.
4. Increasing temperature generally increases the rate constant due to more frequent and energetic collisions between molecules.
5. The Arrhenius equation describes how the rate constant varies with temperature using parameters such as activation energy and frequency factor.

Review Questions

• What are the units of the rate constant for a second-order reaction?
• How does temperature affect the rate constant?
• What role does the rate constant play in determining reaction rates from given concentrations?

Related terms

Rate Law:

An equation that relates the reaction rate to concentrations of reactants, often including a proportionality factor known as the rate constant ($k$).

Activation Energy:

The minimum amount of energy required for reactants to undergo a chemical reaction.

Arrhenius Equation:

A formula that expresses how the rate constant ($k$) changes with temperature: $k = A e^{-E_a/RT}$, where $A$ is the frequency factor, $E_a$ is activation energy, $R$ is the gas constant, and $T$ is temperature.