Using data from Appendix 11, and the value for the standard Gibbs energy of formation for PbS

Question:

Using data from Appendix 11, and the value for the standard Gibbs energy of formation for PbS of −99 kJ mol^–1, determine a value for K_sp for this salt.

Data from Appendix 11

The concentration of each aqueous solution is 1 mol dm⁻³ and the pressure of a gaseous component is 1 bar (10⁵ Pa). (Changing the standard pressure to 1 atm (101 300 Pa) makes no difference to the values of E° at this level of accuracy.) Each half-cell listed contains the specified solution species at a concentration of 1 mol dm⁻³; where the half-cell contains [OH]⁻, the value of E° refers to [OH⁻] = 1 mol dm⁻³, hence the notation E°_{[OH⁻] = 1}