`Ni+H_(2)SO_(4)` (hot and concentrated) `to X(g)`
The liberated gas (select the correct statement)

Options

A. develops blue colour spots on the filter paper moistened with potassium iodate and strach solution
B. turns acidified `K_(2)Cr_(2)O_(7)` solution green
C. produces black precipitate with lead acetate solution
D. reacts with `Cl_(2)` water to produce an acid which gives white fumes with ammonia.

Explanation

To solve the question regarding the reaction of nickel with hot and concentrated sulfuric acid, we will follow these steps:

### Step-by-Step Solution:

1. **Identify the Reaction**:
Nickel (Ni) reacts with hot and concentrated sulfuric acid (H₂SO₄). The general reaction can be written as:
\[ \text{Ni} + \text{H}_2\text{SO}_4 \rightarrow \text{NiSO}_4 + \text{H}_2 \]
However, in the presence of hot and concentrated sulfuric acid, the reaction produces sulfur dioxide (SO₂) instead of hydrogen gas.

2. **Write the Balanced Equation**:
The balanced chemical equation for the reaction is:
\[ \text{Ni} + 2 \text{H}_2\text{SO}_4 \rightarrow \text{NiSO}_4 + \text{SO}_2 + 2 \text{H}_2\text{O} \]
Here, the gas evolved (X) is sulfur dioxide (SO₂).

3. **Analyze the Properties of SO₂**:
We need to evaluate the given statements about the gas (SO₂) to determine which ones are correct.

- **Statement 1**: "It develops blue color spots on filter paper moistened with potassium iodide starch solution."
- This is correct. SO₂ can oxidize iodide ions (I⁻) to iodine (I₂), which forms a blue complex with starch.

- **Statement 2**: "It turns acidified K₂Cr₂O₇ into green color."
- This is also correct. SO₂ reduces the orange dichromate ion (Cr₂O₇²⁻) to green chromium ions (Cr³⁺) in acidic medium.

- **Statement 3**: "It produces black precipitate with lead acetate solution."
- This statement is incorrect. SO₂ does not produce a black precipitate with lead acetate; instead, it forms a white precipitate of lead(II) sulfite.

- **Statement 4**: "It reacts with Cl₂ water to produce an acid which gives white fumes with ammonia."
- This statement is correct. SO₂ reacts with chlorine to produce sulfuric acid (H₂SO₄) and hydrochloric acid (HCl), and HCl gives white fumes when reacted with ammonia.

4. **Conclusion**:
Based on the analysis, the correct statements regarding the gas X (SO₂) are statements 1, 2, and 4.