The photochemical reaction rate of a given substance is influenced by several factors, including temperature, light intensity, and the absorption properties of the reactants. When the temperature increases, the reaction rate typically increases as well. This is because an increase in temperature leads to an increase in the average kinetic energy of the molecules, which in turn increases the number of collisions between the reactant molecules. As a result, the probability of successful collisions i.e., those that lead to a reaction also increases.However, it is important to note that the effect of temperature on photochemical reactions is not as straightforward as it is for thermal reactions. This is because photochemical reactions are initiated by the absorption of light energy photons by the reactant molecules, which can lead to the formation of excited states or the direct breaking of chemical bonds. The relationship between temperature and the rate of a photochemical reaction depends on the specific reaction and the balance between the thermal and photochemical processes involved.The activation energy Ea of a reaction is the minimum amount of energy required for the reactants to overcome the energy barrier and form products. The relationship between temperature and activation energy can be described by the Arrhenius equation:k = Ae^-Ea/RT where k is the rate constant, A is the pre-exponential factor, Ea is the activation energy, R is the gas constant, and T is the temperature in Kelvin.According to the Arrhenius equation, the rate constant k increases with increasing temperature, which means that the reaction rate also increases. However, the effect of temperature on the activation energy itself depends on the specific reaction and its mechanism. In some cases, the activation energy may decrease with increasing temperature, while in others, it may remain relatively constant.In summary, the photochemical reaction rate of a given substance generally increases with an increase in temperature due to the increased kinetic energy of the molecules and the higher probability of successful collisions. The relationship between temperature and activation energy depends on the specific reaction and its mechanism, and can be described by the Arrhenius equation.