Chapter 18, Problem 84IAE

Interpretation Introduction

Interpretation:

The concentration of Pb²⁺ in the saturated solution which is in contact with a mixture of ${\text{PbCl}}_{\text{2}}\left(s\right)$ and ${\text{PbBr}}_{\text{2}}\left(s\right)$ needs to be determined.

Concept introduction:

The solubility of a common cation in a mixture of two slightly soluble substances should be calculated with the concept that both equilibriums equations contain same common ion cation value.

$\begin{array}{l}{\text{PbCl}}_2(\text{s)}\rightleftharpoons {\text{Pb}}^{\text{2+}}(\text{aq)}+2{\text{Cl}}_{}^{-}(\text{aq)}{\text{K}}_{\text{sp2}}=1.7\times {10}^{-5}\\ -x\text{}x+y2x\\ {\text{PbBr}}_2(\text{s)}\rightleftharpoons {\text{Pb}}^{\text{2+}}(\text{aq)}+2{\text{Br}}_{}^{-}(\text{aq)}{\text{K}}_{\text{sp1}}=6.6\times {10}^{-6}\\ -yx+y2y\end{array}$