Question

22. (7 pts) What is the gram solubility (g/L) of copper (II) hydroxide (Cu(OH)₂), K_sp = 2.2 x 10^-20 ? Show
the dissolution equation and K_sp expression.

Answer 1

Cu(OH)₂ dissociate as

Cu(OH)₂ Cu²⁺ + 2OH^-

Ksp = [Cu²⁺] [OH^-]²

Let solubility be S

2.210^-20  = S (2S)²

  = S 4S²

= 4S³

S³ = 2.210^-20 / 4

S³ = 5.510^-21

S = 1.76 10^-7

molar solubility of Cu(OH)₂  = 1.76 10^-7 mol/L

molar mass of Cu(OH)₂  = 98 gm/mol

then gram solubility of  Cu(OH)₂  = 1.76 10^-7 98 = 1.7248 10^-5 g/L