Question

The solubility of $A_2{X}_3$ is ' $y$ ' $M$. Its solubility product is_________

• A. $6y^4$
• B. $64y^4$
• C. $36y^5$
• D. $108y^5$

Answer 1

Answer: (D)

For a sparingly soluble salt of molecular formula $A_2{X}_3$, if solubility in pure water is $yM$ at a given temperature,
$A_2{X}_3\rightleftharpoons 2A^{3+}+3X^{2-}$
$2_{y}M3yM$
Solubility product, $K_{sp}={\left[A^{3+}\right]}^2{\left[X^{2-}\right]}^3=(2y{)}^2+(3y{)}^3$ $=4y^2+27y^3=108y^5{M}^5$