2004 AIPMT EquilibriumSolubility Product Easy Question 8 of 10 in Solubility Product

The solubility product of a sparingly soluble salt $AX_2$ is $3.2 \times 10^{-11}$. Its solubility (in moles/litre) is:-

A $3.1 \times 10^{-4}$
B $2 \times 10^{-4}$
C $4 \times 10^{-4}$
D $5.6 \times 10^{-6}$

The answer is B.

Solution

Let the solubility be s mol/L. $AX_2(s) \rightleftharpoons A^{2+}(aq) + 2X^-(aq)$
$[A^{2+}] = s$ and $[X^-] = 2s$
$K_{sp} = [A^{2+}][X^-]^2 = s(2s)^2 = 4s^3$
$4s^3 = 3.2 \times 10^{-11} \Rightarrow s^3 = 8 \times 10^{-12}$
$s = 2 \times 10^{-4}$ mol/L

Concept Ksp of AB2 type salt

Solubility Product in past papers

10 questions from this chapter have appeared across 10 exam years.