The reaction mechanism for the reaction of methane CH4 with chlorine gas Cl2 to form methyl chloride CH3Cl and hydrogen chloride gas HCl under standard conditions can be described as a radical chain reaction. The mechanism consists of three main steps: initiation, propagation, and termination.1. Initiation:Cl2 2 Cl homolytic cleavage of the Cl-Cl bond 2. Propagation:a CH4 + Cl CH3 + HCl abstraction of a hydrogen atom from methane by a chlorine radical b CH3 + Cl2 CH3Cl + Cl reaction of the methyl radical with chlorine gas 3. Termination:Cl + Cl Cl2 recombination of two chlorine radicals CH3 + CH3 C2H6 recombination of two methyl radicals CH3 + Cl CH3Cl recombination of a methyl radical and a chlorine radical The overall reaction is:CH4 + Cl2 CH3Cl + HClTo determine the rate constant for this reaction using quantum chemical calculations and density functional theory DFT , one would need to perform a series of calculations to obtain the potential energy surfaces and transition states for each step of the reaction mechanism. This would involve using a suitable DFT method and basis set, as well as considering the effects of temperature and pressure on the reaction.Once the potential energy surfaces and transition states are obtained, the rate constants for each elementary step can be calculated using transition state theory or other appropriate methods. The overall rate constant for the reaction can then be determined by combining the rate constants for the individual steps, taking into account the concentrations of the reactants and the relative importance of each step in the reaction mechanism.It is important to note that the rate constant values obtained from quantum chemical calculations and DFT are dependent on the specific method and basis set used, as well as the level of theory employed. Therefore, the rate constant values may vary depending on the computational approach used.