A : `CN^(-)` is pseudohalide .
R : `(CN)_(2)` is pseudohalogen .

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion , then mark (1)
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion , then mark (2)
C. If Assertion is true statement but Reason is false , then mark (3)
D. If both Assertion and Reason are false statements , then mark (4)

Answer

To determine the correctness of the assertion and reasoning provided in the question, we will analyze both statements step by step.

### Step 1: Analyze the Assertion
**Assertion (A):** CN⁻ is a pseudohalide.

1. **Definition of Pseudohalide:** A pseudohalide is an anion that behaves similarly to halides. It typically has a negative charge and can form a hydra-acid with hydrogen and an insoluble salt with silver.

2. **Cyanide Ion (CN⁻):** The cyanide ion has a single negative charge. When it reacts with hydrogen (H⁺), it forms hydrocyanic acid (HCN), which is a hydra-acid. Additionally, when it reacts with silver (Ag⁺), it forms silver cyanide (AgCN), which is insoluble in water.

3. **Conclusion for Assertion:** Since CN⁻ meets the criteria of a pseudohalide, the assertion is true.

### Step 2: Analyze the Reasoning
**Reason (R):** (CN)₂ is a pseudohalogen.

1. **Definition of Pseudohalogen:** A pseudohalogen is a compound that behaves like a halogen, typically being a dimer of a pseudohalide.

2. **Dimer of Cyanide:** The dimer of the cyanide ion (CN⁻) is (CN)₂, which can be represented as two cyanide ions bonded together.

3. **Conclusion for Reasoning:** Since (CN)₂ is indeed a dimer of the pseudohalide CN⁻, it qualifies as a pseudohalogen. Therefore, the reasoning is also true.

### Step 3: Evaluate the Relationship Between Assertion and Reasoning
1. **Correctness of Both Statements:** Both the assertion and reasoning are true.

2. **Explanation Validity:** However, the reasoning does not provide a correct explanation for the assertion. The assertion stands on its own based on the properties of CN⁻, while the reasoning simply states that (CN)₂ is a pseudohalogen without explaining why CN⁻ is a pseudohalide.

### Final Conclusion
- **Both Assertion and Reasoning are true, but the Reasoning is not a correct explanation of the Assertion.**
- Therefore, the correct answer is **Option 2**: Both assertion and reasoning are true, but the reason is not the correct explanation of the assertion.

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