Question

The ksp of cadmium hydroxide, cd(oh)2, is 7.20 × 10-15. calculate the solubility of this compound in g/l.

Answer 1

When the solubility is the amount of solute that dissolved in a unit volume of the solvent.

and when the balanced reaction equation is:

so, by using the ICE table:

            Cd(OH)2(s) ↔  Cd2+  +  2OH- 

initial                               0             0

change                          +X           +2X

Equ                                  X             2X

so the Ksp expression = [Cd2+] [OH-]^2 

and we have Ksp = 7.2 x 10^-15

and when we assume the solubility = X
  
by substitution:

7.2 x 10^-15 = (X) (2X)^2

7.2 x 10^-15 = X*4X^2

7.2 x 10^-15 = 4X^3

∴X = ∛(7.2x10^-15)/4

      = 1.22 x 10^-5 M

∴ the solubility = X = 1.22 x 10^-5 M