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 solve the question, we will analyze the assertion and reasoning provided, and determine their validity.

### Step-by-Step Solution:

1. **Understanding the Assertion:**
- The assertion states that `CN^(-)` (cyanide ion) is a pseudohalide.
- A pseudohalide is defined as a species that exhibits similar properties to halides.

2. **Characteristics of Pseudohalides:**
- Pseudohalides must be univalent (having a valency of one).
- They should form bonds with nitrogen.
- They should form precipitates with silver ions (Ag+).

3. **Evaluating the Assertion:**
- The cyanide ion `CN^(-)` is indeed univalent.
- When `CN^(-)` reacts with `H^+`, it forms hydrogen cyanide (HCN).
- When `CN^(-)` reacts with `Ag^+`, it forms silver cyanide (AgCN), which is a precipitate.
- Therefore, the assertion that `CN^(-)` is a pseudohalide is true.

4. **Understanding the Reasoning:**
- The reasoning states that `(CN)_(2)` (dicyanide) is a pseudohalogen.
- Pseudohalogens are compounds that behave similarly to halogens and can form similar types of compounds.

5. **Evaluating the Reasoning:**
- Dicyanide `(CN)_(2)` can be considered a pseudohalogen because it can form similar compounds and has properties akin to halogens.
- Thus, the reasoning that `(CN)_(2)` is a pseudohalogen is also true.

6. **Conclusion:**
- Both the assertion and reasoning are true.
- However, the reasoning does not correctly explain why `CN^(-)` is a pseudohalide, as it focuses on a different compound.
- Therefore, the correct answer is that both statements are true, but the reasoning is not the correct explanation of the assertion.

### Final Answer:
Both A and R are true, but R is not the correct explanation of A.