Question

Three sparingly soluble salts that have same solubility products are given below
I.$A_{2}X$ II.AX III.$A{X}_3$
Their solubilities in a saturated solution will be such that :

• A. III>II>I
• B. III>I>III
• C. II>III>I
• D. II>I>III

Answer 1

The correct option is D II>I>III

For sparingly soluble salt $AX$, the expression for the solubility and solubility product is $S=(K_{sp}{)}^{\left(\frac{1}{2}\right)}$.
For sparingly soluble salt $A_{2}X$, the expression for the solubility and solubility product is $S=(\frac{K_{sp}}{4}{)}^{\left(\frac{1}{3}\right)}$.
For sparingly soluble salt $A{X}_3$, the expression for the solubility and solubility product is $S=(\frac{K_{sp}}{27}{)}^{\left(\frac{1}{4}\right)}$.
Since the values of the solubility products are same, the decreasing order of the solubility in the saturated solution is $II>I>III$.