Arrhenius equation

This is a relationship between reaction rate, activation energy, and temperature. It is an empirical relationship, but it works remarkably well:

k = Rate constant of reaction
A = Constant, depending on the reaction
R = Molar gas constant
T = Temperature
E_a = activation energy for the reaction

Notice that this shows rate increasing with temperature, and decreasing with activation energy.

Examples will often give you some variables and have you calculate another, usually requiring you to rearrange the equation by making use of logarithm rules.