Question

The Ksp of Al(OH)3 is 2.0 x 10-31 at 298 K. What is \DeltaGo (at 298 K) for the precipitation of Al(OH)3 according to the equation below?
Al3+(aq) + 3OH- (aq) -> Al(OH)3 (s)

Answer 1

ΔG° = -RT ln K

ΔG° = -RT ln 1/Ksp (reverse reaction, solid (Al(OH)₃ not count for equilibrium constant-K)

ΔG° = -RT ln 1/Ksp

ΔG° = -8.314 x 10⁻³ x 298 ln 1/(2 x 10⁻³¹)

ΔG° = -175.132 kJ/mol