Question

Consider a solution of Cu(CH3COO)2. (a) Write any possible chemical reactions that may occur in water and (b) would this solution be acidic, basic or neutral at 25C? Ka for the transitional metal acid is 3x10-8 and the Ka of carbocyclic acid is 1.8x10-5.

Answer 1

Cu(CH3COO)2 is a salt of weak base Cu(OH)2 and weak acid CH3COOH.

The conjugate acid of weak base Cu(OH)2 is Cu2+ (strong)

The conjugate base of weak acid CH3COOH is CH3COO- (strong)

a). Since both Cu2+ and CH3COO- are strong they undergo hydrolysis according to the following equation,

Cu2+(aq) + 2H2O    <-----------> Cu(OH)2(aq) + 2H+(aq)

CH3COO-(aq) + H2O <----------> CH3COOH(aq) + OH-(aq)

given that Ka for the transitional metal acid is 3x10-8 and the Ka of carbocyclic acid is 1.8x10-5.

Kb for the transitional metal acid is 3.34x10-7

c). pH of Cu(CH3COO)2 = 7+1/2[pKa-pKb)

                                     = 7+ 1/2(-log(1.8*10^-5)+log(3.34*10^-7)

                                       = 6.13

the nature of the solution is acidic because pH = 6.13 < 7