Does heat increase reaction rates?

[gkangelexa]

I thought heat increased reaction rates, meaning that when something is at equilibrium, it should increase both the forward and reverse reaction rates...
Is this wrong?

Then why does Le Chatelier's principle predict that a temperature increase favors the endothermic direction?

 

[CJames]

In a reversible reaction, an increase in temperature favors the endothermic direction because there is an excess of heat. A decrease in temperature favors the exothermic direction because there is a relatively low concentration of heat. It increases overall reactions, but it favors one direction because of the concentrations.

 

[Ygggdrasil]

Increasing the temperature of the system will indeed increase both the forward rate of reaction and the reverse rate of reaction. However, the magnitude of the increase will not be equal. The rate of the endothermic reaction will increase more than the rate of the exothermic reaction.

One can see this by looking at the Arrhenius equation, which explains how the rate of a chemical reaction depends on temperature, and by realizing that the endothermic reaction will have a larger activation energy than the exothermic reaction.