The addition of excess potassium cyanide () to an aqueous solution containing and followed by passing gas results in which of the following observations?

Question

The addition of excess potassium cyanide ($KCN$) to an aqueous solution containing $Cu^{2+}$ and $Cd^{2+}$ followed by passing $H_2S$ gas results in which of the following observations?

Prashant Kotian · Accepted Answer

Correct answer: C. Both ions form soluble cyano complexes: and . The copper complex is highly stable ( is very small), providing virtually no free to precipitate. The cadmium complex is less stable, dissociating enough to provide which exceeds the of , yielding a yellow precipitate.

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