Question

If the solubility of an electrolyte is S, then what is the solubility product of the electrolyte of the type $A_3{B}_2$ ?

• A. $6S^3$
• B. $27S^5$
• C. $108S^5$
• D. $36S^5$

Answer 1

Answer: (C)

$A_3{B}_2\rightleftharpoons 3A^{2+}+2B^{3-}$
$K_{sp}=[A^{2+}{]}^3[B^{3-}{]}^2$
If $S$ = solubility of $A_3{B}_2$, then
$[A^{2+}]=3S;[B^{3-}]=2S$
therefore, $K_{sp}=(3S{)}^3\times (2S{)}^2$
          $=27S^3\times 4S^2$
          $=108S^5$