The relationship between standard Gibbs free energy change (ΔG∘) and the equilibrium constant (here, solubility product Ksp) is given by:
ΔG∘=−RTlnKsp=−2.303RTlogKsp
Given:
ΔG∘=+63.3 kJ=63.3×103 J
R=8.314 J K−1mol−1
T=25∘C=298 K
Substituting the values into the equation:
63.3×103=−2.303×8.314×298×logKsp
logKsp=−2.303×8.314×29863300
logKsp=−11.09
Ksp=antilog(−11.09)=10−11.09=100.91×10−12≈8.128×10−12≈8.0×10−12.