AIIMS 2005 Chemistry Sulfur Compounds Assertion Reason Question

To analyze the question, we have to evaluate both the assertion and the reason provided.

Assertion Analysis:

The assertion states that the reaction of sulfur dioxide (SO₂) and hydrogen sulfide (H₂S) in the presence of a Fe₂O₃ catalyst produces elemental sulfur (S). This is indeed true. The reaction can be represented as follows:

$$\text{SO}_2 + 2 \text{H}_2\text{S} \xrightarrow{\text{Fe}_2\text{O}_3} 3 \text{S} + 2 \text{H}_2\text{O}$$

In this reaction, sulfur dioxide acts as an oxidizing agent, while hydrogen sulfide acts as a reducing agent. The presence of the catalyst (Fe₂O₃) facilitates the reaction but does not get consumed in the process.

Reason Analysis:

The reason given states that SO₂ is a reducing agent. However, this is false. In the context of this reaction, SO₂ is actually acting as an oxidizing agent because it gains electrons (is reduced) while H₂S loses electrons (is oxidized). Hence, the assertion is true, but the reason is false.

Correct Answer Justification:

Since the assertion is true but the reason is false, the correct option is C) If assertion is true but reason is false.

Why Option B is Incorrect:

Option B states that both the assertion and reason are true but that the reason is not the correct explanation of the assertion. This is incorrect because the reason itself is false — SO₂ is not a reducing agent.

Why Other Options Are Incorrect:

• Option A: Incorrect, because while the assertion is true, the reason is false, so the reason cannot be the correct explanation.
• Option C: Correctly states that the assertion is true and the reason is false, which is the right choice.
• Option D: Incorrect because the assertion is indeed true.

Summary:

1. Assertion: True — the reaction produces elemental sulfur.
2. Reason: False — SO₂ is not a reducing agent; it is an oxidizing agent in this context.
3. Correct Answer: C — the assertion is true, but the reason is false.

Thus, the correct answer is C.