The reaction between hydrogen gas H2 and chlorine gas Cl2 in the gas phase is a radical chain reaction that produces hydrogen chloride HCl . The overall reaction is:H2 + Cl2 2 HClThe reaction mechanism consists of three main steps:1. Initiation: The chlorine molecules absorb energy usually in the form of light and dissociate into chlorine radicals.Cl2 2 Cl2. Propagation: The chlorine radicals react with hydrogen molecules to form hydrogen chloride and hydrogen radicals. Then, the hydrogen radicals react with chlorine molecules to form hydrogen chloride and regenerate chlorine radicals.Cl + H2 HCl + HH + Cl2 HCl + Cl3. Termination: The reaction terminates when two radicals react with each other, forming stable molecules.Cl + Cl Cl2H + H H2H + Cl HClThe rate-determining step is the slowest step in the reaction mechanism, which is the propagation step involving the reaction between the chlorine radical and the hydrogen molecule:Cl + H2 HCl + HThe temperature affects the reaction rate by increasing the kinetic energy of the molecules. As the temperature increases, the molecules move faster, leading to more frequent and energetic collisions between the reactants. This results in a higher reaction rate. According to the Arrhenius equation, the reaction rate constant k is related to the temperature T by the following equation:k = Ae^-Ea/RT where A is the pre-exponential factor, Ea is the activation energy, R is the gas constant, and T is the temperature in Kelvin. As the temperature increases, the exponential term becomes larger, leading to an increase in the reaction rate constant and thus a faster reaction rate.