Question

Determine the equilibrium constant for dissolution of covellite [CuS(s)] by the following reaction at 5, 25, and 35 deg C. CuS(s) + H+ ↔ Cu2+ + HS-

Answer 1

dGo for the reaction,

dGo = dGo(products) - dGo(reactants)

        = (66 + 12) - (-53.6)

        = 131.6 kJ/mol

Using,

dGo = -RTlnK

K = equilibrium constant

R = gas constant

T = 5 + 273 = 278 K

we get,

131600 = -8.314 x 278 lnK

K = 1.87 x 10^-25

When

T = 25 + 273 = 298 K

we get,

131600 = -8.314 x 298 lnK

K = 8.55 x 10^-24

When

T = 35 + 273 = 308 K

we get,

131600 = -8.314 x 308 lnK

K = 4.80 x 10^-23