Question

find the solubility of cui in 0.20 m kcn solution. the ksp of cui is 1.1??10?12 and the kf for the cu(cn)2? complex ion is 1??1024.

Answer 1

$\mathrm{CuI\rightleftharpoons Cu^++I^-\qquad K_{sp}=1.1\times 10^{-12}}\\ \mathrm{Cu^++2CN^-\rightleftharpoons [Cu(CN)_2]^-\qquad K_{f}=1\times 10^{24}}\\ \mathrm{CuI+2CN^-\rightleftharpoons [Cu(CN)_2]^-+I^-}\\ K=K_{sp}K_f\\ =1.1\times 10^{-12}\times 1\times 10^{24}\\ =1.1\times 10^{12}\\ \begin{array}{c c c c c c c} CuI&+&2CN^-&\rightleftharpoons &[Cu(CN)_2]^-&+&I^-\\ &&0.2&&0&&0\\ &&\approx 0&&0.1&&0.1\\ \end{array}\\ \begin{array}{c c c c c} CuI&\rightleftharpoons &Cu^+&+&I^-\\ &&0&&0.1\\ &&s&&0.1+s\approx 0.1 \end{array}\\ s\times 0.1=K_{sp}=1.1\times 10^{-12}\\ \Rightarrow s=1.1\times 10^{-11}M$