Calculating the activation energy and reaction rate constant for the Cl + CH4 -> HCl + CH3 reaction at 298 K using quantum chemical methods requires specialized software and computational resources. However, I can provide you with some general information and an example of how these calculations can be performed.The activation energy Ea is the minimum energy required for a chemical reaction to occur. It can be calculated using quantum chemical methods such as density functional theory DFT or ab initio methods like coupled-cluster CC or Mller-Plesset perturbation theory MP2 . These methods involve solving the Schrödinger equation for the molecular system and determining the energy of the reactants, products, and transition state.Once the activation energy is calculated, the reaction rate constant k can be determined using the Arrhenius equation:k = Ae^-Ea/RT where A is the pre-exponential factor, R is the gas constant 8.314 J/molK , T is the temperature in Kelvin 298 K in this case , and Ea is the activation energy.For example, let's say you have calculated the activation energy for the Cl + CH4 -> HCl + CH3 reaction to be 25 kJ/mol using quantum chemical methods. You can then calculate the reaction rate constant at 298 K using the Arrhenius equation:k = Ae^-25000 J/mol / 8.314 J/molK 298 K To determine the pre-exponential factor A , you would need experimental data or additional computational methods, such as transition state theory.Please note that the activation energy and reaction rate constant values provided in this example are for illustrative purposes only and may not represent the actual values for the Cl + CH4 -> HCl + CH3 reaction. To obtain accurate values, you would need to perform the quantum chemical calculations using appropriate software and computational resources.