You have found Ksp to be 3.4 × 10⁻¹⁰. If solid In₂(SO₄)₃ is added to a solution that already contains 0.150 M In(NO₃)₃, what will the new solubility of the solid be?

Answer 1

When adding In(NO₃)₃ we are adding a common ion, namely the In^3- ion. The contribution of In^3- from the In₂(SO₄)₃ will be insignificant compared to the 0.150 M In^3- coming from the In(NO₃)₃.

In₂(SO₄)₃(s) <==> 2In^3-(aq) + 3SO₄^2-(aq)

Ksp = 3.4x10^-10 = [In^3-]²[SO₄^2-]³

3.4x10^-10 = [0.150]² [SO₄^2-]³

[SO₄^2-]³ = 1.51x10^-8

[SO₄^2-] = 2.47x10^-3 M

Since each mole In₂(SO₄)₃ provides 3 moles SO₄^2- , the estimated solubility of In₂(SO₄)₃ under these conditions would be ~ 1/3 x 2.47x10^-3 M = 8.23x10^-4 M