According to Gibbs free energy and assume constant pressure (Helmholtz ΔG=ΔGΘ+RTln(K)Where K is the equilibrium constant.
At equilibrium ΔG=0:
0=ΔGΘ+RTln(K)→ΔGΘ=−RTln(K)
Solve for the equilibrium constant:
−ΔGΘRT=ln(K)[P][S]=K=exp(−ΔGΘRT)
using this equationJust put into the equation and calculate the equilibrium constant K.
hope it helps