The rates of chemical reactions are usually affected by both temperature and pressure. The effect of temperature on the rate of a chemical reaction is measured as the activation energy. For thermally activated reactions (no tunneling 3 involved), the larger the activation energy 𝐸 ! , the greater the increase in the reaction rate with temperature. Activation energies are measured experimentally by treating the temperature dependence of the rate constant using the Arrhenius equation. The activation energy is the slope of the plot of 𝑙𝑛𝑘 vs 1/𝑇, 𝐸 ! = 𝑅 * "#$% "('/)) + + , where 𝑘 is the rate constant, 𝑇 the temperature, 𝑅 the ideal gas constant, and 𝑝 the pressure.