Given the following standard reduction potentials,

Fe^2+(aq) + 2e^- ==> Fe(s) E naught = -o.440V

FeS(s) + 2e^- ==> Fe(s) + s^2-(aq) E naught = -1.010V

determine the Ksp for FeS(s) at 25 degrees Celsius

Fe(s) ==> Fe^2+ + 2e^- (oxidation)
FeS(s) + 2E^- ==> Fe(s) + S^2-(aq) (reduction)

net reaction: FeS(s) + Fe(s) ==> Fe^2+(aq) + S^2-(aq) + Fe(s)

(-1.010V) - (-0.440V) = -.57

lnk = (1)(-0.57v)/(0.257v)

Ksp = e^-22.5 = 1.8x10^-10