Question

1)The Ksp of nickel(II) hydroxide, Ni(OH)2, is 5.84 × 10-16. Calculate the solubility of this compound in g/L.

2)The Ksp of CaSO4 is 4.93× 10–5. Calculate the solubility (in g/L) of CaSO4(s) in 0.350 M Na2SO4(aq) at 25 °C.

Answer 1

1)

Ni(OH)2 <------------------> Ni+2 + 2 OH-

                                             S           2S

Ksp = [Ni+2][OH-]^2

5.84 × 10^-16 = S x (2S)^2

5.84 × 10^-16 = 4S^3

S = 5.27 x 10^-6 M

solubility = 5.27 x 10^-6 x 92.7

solubility = 4.88 x 10^-4 g/L

2)

CaSO4 <---------------> Ca+2 + SO42-

                                         S           0.350

Ksp = [S][0.350]

4.93× 10^–5 = S x 0.350

S = 1.408 x 10^-4 M

solubility = 1.408 x 10^-4 x 136.14

              = 0.0192 g/L