In: Chemistry
Standard reduction potentials are provided for two half reactions that involve the hypothetical metal "M" and sulfide ion. Use them to calculate the value of the solubility product constant for the metal sulfide. (Hint: what is the balanced chemical reaction equation for the equilibrium reaction that gives Ksp?)
M2+ + 2 e- ⇌ M(s) | Eo = -0.057 V |
MS(s) + 2 e- ⇌ M(s) + S2- | Eo = -1.208 V |
Ksp of MS(s) = |
Oxidation : M (s) <---------> M2+ + 2e- Eo = -0.057 V
Reduction : MS(s) + 2 e- <------------> M(s) + S2- Eo = - 1.208 V
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Overall : MS(s) <------------> M2+ + S2-
balanced chemical reaction : MS(s) <------------> M2+ + S2-
Eocell = - 1.208 + 0.057
= - 1.151 V
delta Go = - n F Eocell
= - 2 x 96485 x - 1.151
= 222108.5 J
delta Go = - RT ln Ksp
222108.5 = - 8.314 x 298 x ln Ksp
Ksp = 1.17 x 10^-39
Ksp of MS (s) = 1.2 x 10-39