lodine crystals are added to liquor ammonia and the brown precipitate so formed is separated , dried and spread on floor. On walking over the precipitate harmless explosion occurs releasing coloured gas. The ppt. and coloured gas are respectively

Options

A. `NI_3,I_2`
B. `NH_4I and I_2`
C. `NH_3NI_3,I_2`
D. `NH_3NI_3,I_2O_5`

Answer

To solve the question, we need to identify the brown precipitate formed when iodine crystals are added to liquid ammonia and the colored gas released during the harmless explosion when walking over the precipitate.

### Step-by-Step Solution:

1. **Understanding the Reaction**:
- When iodine (I2) is added to liquid ammonia (NH3), a complex is formed. The reaction can be represented as:
\[ I_2 + NH_3 \rightarrow [NI_3] \cdot NH_3 \]
- This complex is known as nitrogen triiodide-ammonia complex.

2. **Formation of Brown Precipitate**:
- The compound formed, nitrogen triiodide (NI3), is known to be unstable and is responsible for the brown precipitate observed. Thus, the brown precipitate is:
\[ \text{Brown precipitate} = NI_3 \cdot NH_3 \]

3. **Decomposition of the Precipitate**:
- When the brown precipitate (NI3) is disturbed (for example, by walking over it), it decomposes explosively, releasing nitrogen gas (N2) and iodine gas (I2):
\[ 2NI_3 \rightarrow N_2 + 3I_2 \]
- The nitrogen triiodide decomposes into nitrogen gas and iodine gas.

4. **Identifying the Colored Gas**:
- The gas released during this decomposition is iodine (I2), which is known for its characteristic purple or violet color.

5. **Final Answer**:
- Therefore, the brown precipitate is nitrogen triiodide (NI3) and the colored gas released is iodine (I2).

### Summary:
- **Brown Precipitate**: Nitrogen triiodide (NI3)
- **Colored Gas**: Iodine (I2)