Question

What is the correct representation for the solubility product of $Sn{S}_2$ ?

• A. $\left[S{n}^{2+}\right]{\left[S^{2-}\right]}^2$
• B. $\left[S{n}^{4+}\right]{\left[S^{2-}\right]}^2$
• C. $\left[S{n}^{2+}\right]\left[2S^{2-}\right]$
• D. $\left[S{n}^{2+}\right]{\left[2S^{2-}\right]}^2$

Answer 1

Answer: (A)

$Sn{S}_2+aq\rightleftharpoons \underset{\text{ solution }}{Sn{S}_2}\rightleftharpoons S{n}^{2+}+2S^{2-}$
Applying law of mass action to this equilibrium
$K=\frac{\left[S{n}^{2+}\right]{\left[S^{1-}\right]}^2}{\left[Sn{S}_2\right]}$
Or $K{\left[Sn{S}_2\right]}_4=\left[S{n}^{2+}\right]{\left[S{n}^{2-}\right]}^2$
since $\left[Sn{S}_2\right]$, in solid state remain constant and therefore,
$K_{sp}=\left[S{n}^{2+}\right]{\left[S^{2-}\right]}^2$