1. 3S + 2H₂SO₄ → 3SO₂ + 2H₂O 2. C + 2H₂SO₄ → CO₂ + 2SO₂ + 2H₂O 3. CaF₂ + H₂SO₄ → CaSO₄ + 2HF 4. Cu + 2H₂SO₄ → CuSO₄ + SO₂ + 2H₂O

Answer: 3. CaF₂ + H₂SO₄ → CaSO₄ + 2HF Key idea: oxidising behaviour means H₂SO₄ is reduced (S goes from +6 to +4 as SO₂ ). Options 1, 2, 4: SO₂ is formed, so H₂SO₄ oxidises S, C and Cu. Option 3: CaF₂+H₂SO₄→ CaSO₄+2HF is only an acid displacement of a weaker, volatile acid; no oxidation-state change.

Topic: General trends, Group 15 and 16· p-Block Elements

Hot concentrated sulphuric acid is a moderately strong oxidizing agent. Which of the following reactions does not show oxidizing behaviour?

1. \(3S + 2H_2SO_4 \rightarrow 3SO_2 + 2H_2O\)

2. \(C + 2H_2SO_4 \rightarrow CO_2 + 2SO_2 + 2H_2O\)

3. \(CaF_2 + H_2SO_4 \rightarrow CaSO_4 + 2HF\)

4. \(Cu + 2H_2SO_4 \rightarrow CuSO_4 + SO_2 + 2H_2O\)

Doubtly Asked 30 Oct 2026 NEET UG 2016 Phase 2 neet Save WhatsApp Report

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Answer: 3. \(CaF_2 + H_2SO_4 \rightarrow CaSO_4 + 2HF\)

Key idea: oxidising behaviour means \(H_2SO_4\) is reduced (S goes from +6 to +4 as \(SO_2\)).

Options 1, 2, 4: \(SO_2\) is formed, so \(H_2SO_4\) oxidises S, C and Cu.
Option 3: \(CaF_2+H_2SO_4\rightarrow CaSO_4+2HF\) is only an acid displacement of a weaker, volatile acid; no oxidation-state change.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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Hot concentrated sulphuric acid is a moderately strong oxidizing agent. Which of the following reactions does not show oxidizing behaviour?

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