2. The forward rate constant for the elementary reaction               C2H6(g)→ 2 CH3(g) is 0.00157 s-1 at 1000 K. What is the rate constant for the backward reaction at this temperature ? For CH3(g) and C2H6(g) the standard Gibbs free energies of formation are 159.74 kJ/mol and 109.55 kJ/mol, respectively, at 1000 K.