White substance dissolves in hot water. A black precipitate appears on passing `H_(2)S` gas in its aqueous solution. The black precipitate dissolves in hot `HNO_(3)`. A white precipitate is obtained on adding concentrated `H_(2)SO_(4)` in its solution. This white precipitate is of

Options

A. `BaSO_(4)`
B. `SrSO_(4)`
C. `PbSO_(4)`
D. `CdSO_(4)`

Answer

To solve the problem step by step, we will analyze the information provided in the question and relate it to the chemical reactions involved.

### Step 1: Identify the white substance
The question states that a white substance dissolves in hot water. This suggests that the substance is likely a salt that is soluble in water. A common example of a white substance that fits this description is lead(II) nitrate, \( \text{Pb(NO}_3\text{)}_2 \).

**Hint:** Look for common soluble salts that are white in color.

### Step 2: Reaction with H₂S
When hydrogen sulfide gas (\( \text{H}_2\text{S} \)) is passed through the aqueous solution of the white substance, a black precipitate forms. The black precipitate is likely lead(II) sulfide (\( \text{PbS} \)), which is known to form when \( \text{H}_2\text{S} \) reacts with lead(II) ions.

**Hint:** Identify the precipitate formed from the reaction of sulfide ions with lead(II) ions.

### Step 3: Dissolution in hot HNO₃
The black precipitate (\( \text{PbS} \)) dissolves in hot nitric acid (\( \text{HNO}_3 \)). This reaction can be represented as:
\[ \text{PbS} + 4 \text{HNO}_3 \rightarrow \text{Pb(NO}_3\text{)}_2 + 2 \text{NO} + 2 \text{H}_2\text{O} + \text{S} \]
This confirms that the black precipitate is indeed lead(II) sulfide.

**Hint:** Consider the solubility of sulfides in strong acids.

### Step 4: Reaction with concentrated H₂SO₄
Next, when concentrated sulfuric acid (\( \text{H}_2\text{SO}_4 \)) is added to the solution containing lead(II) nitrate, a white precipitate forms. The reaction can be written as:
\[ \text{Pb(NO}_3\text{)}_2 + \text{H}_2\text{SO}_4 \rightarrow \text{PbSO}_4 + 2 \text{HNO}_3 \]
The white precipitate formed is lead(II) sulfate (\( \text{PbSO}_4 \)), which is known to be insoluble in water.

**Hint:** Look for common precipitates formed from the reaction of sulfates with metal ions.

### Conclusion
Based on the reactions and the observations made, the white precipitate obtained upon adding concentrated sulfuric acid to the solution is lead(II) sulfate (\( \text{PbSO}_4 \)).

**Final Answer:** The white precipitate is \( \text{PbSO}_4 \) (lead(II) sulfate).