Question

Assertion (A): \( \text{Cu}^{2+} \) and \( \text{Cd}^{2+} \) are separated by first adding KCN solution and then passing H\(_2\)S gas. Reason (R): KCN reduces \( \text{Cu}^{2+} \) to \( \text{Cu}^+ \) and forms a complex with it.

• A. Both (A) and (R) are true and (R) is the correct explanation of (A)
• B. Both (A) and (R) are true but (R) is not the correct explanation of (A)
• C. (A) is true but (R) is false
• D. (A) is false but (R) is true

Hint:

KCN reduces \( \text{Cu}^{2+} \) to \( \text{Cu}^+ \), and H\(_2\)S is used to precipitate \( \text{CdS} \) from \( \text{Cd}^{2+} \).

Answer 1

The Correct Option is B

Step 1: Understand the reaction.
KCN reduces \( \text{Cu}^{2+} \) to \( \text{Cu}^+ \), and this complex formation aids in the separation of \( \text{Cu}^{2+} \) and \( \text{Cd}^{2+} \) by selective precipitation using H\(_2\)S gas.
Step 2: Conclusion.
Thus, the assertion is true, but the reason is not a complete explanation for the separation.
Final Answer: \[ \boxed{B} \]