Question

If the salts $M_2X$ , $QY_2$ and $PZ_3$ have the same solubilities, their $K_{sp}$ values are related as

• A. $K_{sp}(M_2K) = K_{sp}(QY_2 ) < K_{sp}(PZ_3)$
• B. $K_{sp}(M_2X) > K_{sp}(QY_2) = K_{sp}(PZ_3)$
• C. $K_{sp}(M_2X) = K_{sp}(QY_2) > K_{sp}(PZ_3)$
• D. $K_{sp} (M_2X) > K_{sp} (QY_2) > K_{sp} (PZ_3)$

Answer 1

Answer: (A)

$K_{sp}(M_2K) = K_{sp}(QY_2 ) < K_{sp}(PZ_3)$

Answer 2

For $M_2 - X$;
$M_2X {<=>} 2M^+ + X^{2-}$
$\therefore K_{sp} = (2s)^2 \times s$
$= 4s^2$
For $QY_2$;
$QY_2 {<=>}Q^{2+} + 2Y^-$
$\therefore K_{sp} = s \times (2s)^2 = 4s^2$
$PZ_3$;
$PZ_3 {<=>} P^3 + 3Z^-$
$\therefore, K_{sp} = s \times (3s)^3 = 27 s^4$
Thus, $K_{sp}$ is in order,
$K_{sp}(M_2X) = K_{sp} (QY_2) < K_{sp}(PZ_3)$