The variable k is the rate constant, which is dependent on the frequency of the collisions f, orientation factor p, activation energy Ea, and temperature T. From the expression for the Arrhenius equation you should note that a small increase in activation energy leads to a large decrease in rate constant. Furthermore, temperature has a similarly exponential effect on the rate constant. An experimental rule of thumb is that a 10oC increase in temperature leads to a doubling of the rate constant.