Question

Determine the concentration of Cu2+ and OH- present in a saturated Cu(OH)2 solution. Will the solubility change with the addition of acid? If so, will it increase or decrease?

Answer 1

i) Solubility equillibrium of Cu(OH)₂ is

Cu(OH)₂(s) <------> Cu²⁺(aq) + 2OH^-(aq)

Ksp = [Cu²⁺][OH^-]² = 2.20×10^-20M²

If solubility of Cu(OH)2 is represented as S

[Cu²⁺] = S

[OH-] = 2S

Therefore,

S × (2S)² = 2.20×10^-20

4S³ = 2.20×10^-20

S = 1.77×10^-7

Therefore,

[Cu²⁺] = 1S= 1.77×10^-7M

[OH^-] = 2S = 3.54×10^-7M

ii) Yes, Solubility will change with addition of acid

Solubility will increase with addition of acid

the OH^- ion react with H⁺ ion so, the equillbrium will shift to the right.Thus the solubility of Cu(OH)2 increase with the addition of acid.