Question

Determine solubility of $AgBr$ in a $0.1\, M \,KCN$ solution.
$\left[K_{f}\right.$ of $\left[ Ag ( CN )_{2}\right]^-=5.6 \times 10^{8} ; K_{ sp }$ of $\left.AgBr =7.7 \times 10^{-13}\right]$

• A. $ 2\times 10^{3}M $
• B. $ 4\times 10^{-6}M $
• C. $ 2\times 10^{-6}M $
• D. $ 4\times 10^{-3}M $

Answer 1

Answer: (A)

$\underset{0.1-2 s}{AgBr +2 CN ^{-}} \rightleftharpoons \underset{s}{Ag} ( CN )_{2}^{-}\underset{s}{+} Br ^{-}$
$K_{ sp }=k_{ sp } \cdot k=4.3 \times 10^{-4}$
$4.3 \times 10^{-4}=\left(\frac{s}{0.1-2 s}\right)$
$s=2 \times 10^{-3}$