Question

Calculate the solubility of NiCO3 in moles per liter and grams per liter (Ksp = 1.4 x 10-7)

Answer 1

NiCO₃ --> Ni²⁺ + CO₃^2-

Since 1 formula unit of NiCO₃ produces 2 ions, the formula for molar solubility (s) is

$K_{sp}=s^2$

Therefore,

$s=\sqrt{K_{sp}}=\sqrt{1.4\times10^{-7}}=3.74\times10^{-4}\space{mol/L}$

To find the solubility in grams per liter, s should be multiplied by the molar mass:

$3.74\times10^{-4}\frac{mol}{L}\times118.7\frac{g}{mol}=0.0444\space{g/L}$

Answer: $3.74\times10^{-4}\space{mol/L}$ ; 0.0444 g/L