The rate of reaction depends on both the rate constant and the concentration of the reactants. rate = k [NO] 2 [O2] . The larger the value of k the faster the reaction. If the temperature is increased, the molecules have more energy. There are more frequent collisions and more of the collisions have more energy than the activation energy. If the concentrations stay the same and the rate increases with temperature, then k (the rate constant) must increase with temperature. For many reactions the rate doubles with every 10 °C increase in temperature.