In: Chemistry
14. From the half-reactions below, calculate the solubility product of Mg(OH)2.
Mg2+ + 2e º Mg(s) E° = -2.360 V
Mg(OH)2(s) + 2e º Mg(s) + 2OH- E° = -2.690 V
oxidation :anode
Mg(s) --------------------> Mg2+ + 2e º E° = -2.360 V
reduction : cathode
Mg(OH)2(s) + 2e º -------------------->Mg(s) + 2OH- E° = -2.690 V
E° = E cathode - E anode
= -2.690 + 2.360
= -0.33
over all reaction
Mg(OH)2(s) -------------------> Mg2+ + 2 OH-
Ecell = Eo cell - 0.0591 / n * log [Mg+2] [OH-]^2
0 = Eo cell - 0.0591 / n * log [Mg+2] [OH-]^2
Eo cell = 0.0591 / n * log [Mg+2] [OH-]^2
Eo cell = 0.0591 / 2 * log Ksp
-0.33 = 0.0591 / 2 * log Ksp
log Ksp = -11.17
Ksp = 6.76 x 10^-12
solubility product = Ksp = 6.76 x 10^-12