A: Primary aliphatic amines react with `CS_(2)` and `HgCl_(2)` give precipitate of Hgs.
R: Secondary amine does not give precipitate of Hgs in this reaction.

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 reason statements regarding the reaction of primary and secondary aliphatic amines with carbon disulfide (CS₂) and mercury(II) chloride (HgCl₂).

### Step-by-Step Solution:

1. **Understanding the Reaction of Primary Amines**:
- Primary aliphatic amines react with carbon disulfide (CS₂) and mercury(II) chloride (HgCl₂).
- The reaction produces alkyl isothiocyanate, mercury sulfide (HgS), and hydrochloric acid (HCl).
- The formation of HgS is significant because it is an insoluble precipitate, which indicates that the reaction has occurred.

2. **Identifying the Reaction of Secondary Amines**:
- Secondary amines, when treated with CS₂ and HgCl₂, do not produce HgS.
- Instead, secondary amines react with CS₂ to form isothiocyanate, but they do not react further with HgCl₂ to produce the precipitate of HgS.
- This lack of reaction is due to the presence of two alkyl groups in secondary amines, which prevents the formation of the necessary intermediate that would lead to HgS precipitation.

3. **Conclusion on the Assertion and Reason**:
- The assertion (A) states that primary aliphatic amines react with CS₂ and HgCl₂ to give a precipitate of HgS, which is correct.
- The reason (R) states that secondary amines do not give a precipitate of HgS in this reaction, which is also correct.
- However, while both statements are true, the explanation provided in the reason does not accurately describe why secondary amines do not produce HgS, as it does not detail the reaction mechanism involved.

4. **Final Answer**:
- Both the assertion and the reason are correct, but the reason does not correctly explain the assertion. Therefore, the correct option would be that both statements are true, but the reason is not a valid explanation for the assertion.