A solution containing and is treated with excess . When is passed through the resulting solution, wh — Qualitative and Quantitative Analysis Chemistry Question
Question
A solution containing $Cu^{2+}$ and $Cd^{2+}$ is treated with excess $KCN$. When $H_2S$ is passed through the resulting solution, which of the following happens?
Answer: C
💡 Solution & Explanation
Both form soluble cyano complexes. The $[Cu(CN)_4]^{3-}$ complex is highly stable and gives no free $Cu^+$ to precipitate. The $[Cd(CN)_4]^{2-}$ complex is less stable, dissociates slightly, and allows yellow $CdS$ to precipitate.
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