Finding value of equilibrium constant
$\Delta G=\Delta H - T \Delta S = 250-48 \times 10^{-3} \times 500 = 226 KJ/mol$
$K=exp(-\frac{\Delta G}{RT})=exp(-\frac{226 \times 10^3}{8.314 \times 500})=2.45 \times 10^{-24}$