Ammonium salts on heating with slaked lime liberates a colourless gas `(X)`. Identify the correct statement for gas `(X)` and ammonium salt.

Options

A. It turns red litmus blue and gives yellow ppt. with `Na_(3)[Co(NO_(2))_(6)]`
B. It turns filter paper moistened with mercurous nitrate black and gives intense blue coloured solution with `CuSO_(4)(aq)`
C. It when passed through Nessler reagent produces a brown colour ppt.
D. All of these

Explanation

To solve the question regarding the reaction of ammonium salts with slaked lime and the properties of the gas produced, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reaction**:
Ammonium salts, such as ammonium chloride (NH₄Cl), react with slaked lime (calcium hydroxide, Ca(OH)₂) upon heating. The general reaction can be written as:
\[ 2 NH_4Cl + Ca(OH)_2 \rightarrow CaCl_2 + 2 NH_3 + 2 H_2O \]
Here, ammonia (NH₃) is the colorless gas (X) that is liberated.

2. **Identify the Gas (X)**:
The gas produced in this reaction is ammonia (NH₃). It is colorless and has a characteristic pungent smell.

3. **Determine the Properties of Ammonia**:
- Ammonia is basic in nature. It can turn red litmus paper blue, indicating its basicity.
- When ammonia gas is passed through moist mercurous nitrate (Hg₂(NO₃)₂), it produces a black precipitate of mercury(I) oxide (HgO) and other products.
- Ammonia reacts with copper(II) sulfate (CuSO₄) to form a deep blue complex, known as tetraamminecopper(II) sulfate.

4. **Reactions with Nessler's Reagent**:
Ammonia reacts with Nessler's reagent (K₂HgI₄) to produce a brown precipitate, indicating the presence of ammonia.

5. **Conclusion**:
All the statements regarding the properties and reactions of ammonia gas (X) and ammonium salts are correct. Therefore, the best answer is option D: "All of these."