15.已知反应:-|||-.dfrac (1)(2)(H)_(2)(g)+dfrac (1)(2)(Cl)_(2)(g)leftharpoons HCl(g)-|||-在298.15K时的 _(1)=4.9times (10)^16 ,_(r)(m)_(m)(298.15K)=-92.31kJcdot (mol)^-1 ,求在500K时的Kg^2。