Question

One of the most obvious ways to tell that a chemical reaction has occurred, as we all know, is that the color of 'stuff' changes. Ligand exchange reactions are one class of reactions where this is very evident, as exemplified by the color change of a green Ni(H2O)62+ solution to the yellow-green of a NiCl64- solution with the substitution of H2O ligands for Cl- ligands.

Ni(H2O)62+ (aq) + 6 Cl- (aq) equilibrium arrow NiCl64- (aq) + 6 H2O (l)

The equilibrium constant for this reaction is 1.0 x 109. Calculate the change in Gibbs free energy for the reaction at 400 K in kJ mol-1. (Note R = 8.314 J mol-1 K-1)

Answer 1

delta G = -RT*lnK

Answer 2

nkllj;