Question

A solution contains 0.10 m sodium cyanide and 0.10 m potassium hydroxide. solid zinc acetate is added slowly to this mixture. what is the formula of the substance that precipitates first?

Answer 1

1) Zn(CH₃COO)₂(s) + 2KOH(aq) = Zn(OH)₂(s) + 2CH₃COOK(aq)

Ksp{Zn(OH)₂}=1.2*10⁻¹⁷

2) Zn(CH₃COO)₂(s) + 2NaCN(aq) = Zn(CN)₂(s) + 2CH₃COONa(aq)

Ksp{Zn(CN)₂}=2.6*10⁻¹³


Ksp{Zn(OH)₂}<Ksp{Zn(CN)₂}

Zn(OH)₂ precipitates first