Arrhenius equation

Definition

The Arrhenius equation describes the temperature dependence of reaction rates. It shows how the rate constant $k$ increases exponentially with an increase in temperature.

5 Must Know Facts For Your Next Test

1. The formula for the Arrhenius equation is $k = A e^{-E_a/(RT)}$, where $k$ is the rate constant, $A$ is the pre-exponential factor, $E_a$ is the activation energy, $R$ is the gas constant, and $T$ is the temperature in Kelvin.
2. A higher activation energy ($E_a$) means that fewer molecules have enough energy to react at a given temperature.
3. The pre-exponential factor (A) represents the frequency of collisions with proper orientation for reaction.
4. The Arrhenius equation can be rearranged to $\ln(k) = \ln(A) - \frac{E_a}{R} \cdot \frac{1}{T}$ for easier plotting and calculation of $E_a$ from experimental data.
5. An important concept related to this equation is that even a small increase in temperature can significantly increase the reaction rate.

Review Questions

• What does each term in the Arrhenius equation represent?
• How does an increase in temperature affect the rate constant according to the Arrhenius equation?
• What information can you derive from a plot of $\ln(k)$ versus $\frac{1}{T}$?

Related terms

Activation Energy:

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

Rate Constant:

A proportionality constant in the rate law that provides a measure of how quickly a reaction occurs.

Pre-exponential Factor: Also known as frequency factor, it represents how often molecules collide with correct orientation per unit time.