Mixture is heated with dil. `H_(2)SO_(4)` and the lead acetate paper turns black by the evolved gases. The mixture contains

Options

A. Sulphite
B. Sulphide
C. Sulphate
D. Thiosulphate

Explanation

To solve the question, we need to analyze the information provided about the reaction of a mixture with dilute sulfuric acid (H₂SO₄) and the resulting blackening of lead acetate paper. Here’s a step-by-step breakdown of the solution:

### Step-by-Step Solution:

1. **Understanding the Reaction**:
- When a mixture is heated with dilute H₂SO₄, it can produce gases. One important gas that can be evolved in such reactions is hydrogen sulfide (H₂S).
- Lead acetate paper is used to detect the presence of hydrogen sulfide gas. When H₂S comes into contact with lead acetate, it forms lead sulfide (PbS), which is a black precipitate.

2. **Identifying the Blackening of Lead Acetate Paper**:
- The blackening of lead acetate paper indicates that hydrogen sulfide gas is present. This occurs because H₂S reacts with lead acetate (Pb(CH₃COO)₂) to form lead sulfide (PbS) and acetic acid (CH₃COOH).
- The reaction can be summarized as follows:
\[ Pb(CH₃COO)₂ + H₂S \rightarrow PbS (black \, ppt) + 2 CH₃COOH \]

3. **Conclusion about the Mixture**:
- Since the blackening of the lead acetate paper is due to the formation of lead sulfide, we can conclude that the mixture must contain a source of hydrogen sulfide.
- The presence of hydrogen sulfide in the mixture suggests that it contains sulfide ions (S²⁻).

4. **Final Answer**:
- Therefore, the mixture contains sulfide, which leads us to conclude that the correct answer is that the mixture contains sulfide.