Textbook Problem

The overall formation constant for HgI₄²⁻ is 1.0 × 10³⁰. That is,

$1.0\times {10}^{30}=\frac{[Hg{I}_4{}^{2-}]}{[H{g}^{2+}]{[I^{-}]}^4}$

What is the concentration of Hg²⁺ in 500.0 mL of a solution that was originally 0.010 M Hg²⁺ and 0.78 M I⁻? The reaction is

${\text{Hg}}^{\text{2+}}(aq)+4{\text{I}}^{-}(aq)\rightleftharpoons Hg{I}_4{}^{2-}(aq)$