Halide oxidation via displacement or acid reaction

Steps:

• Identify oxidation of halide as loss of electron from X⁻ to X₂.
• Check each mixture for a stronger oxidant displacing weaker halide or acid oxidizing halide.
• Verify both parts of row cause X⁻ → X₂.
• Eliminate rows where only one or neither oxidizes.

Why D is correct:

• Br₂ oxidizes I⁻ (Br₂ + 2I⁻ → 2Br⁻ + I₂); conc. H₂SO₄ oxidizes Br⁻ via 2NaBr + H₂SO₄ → Na₂SO₄ + Br₂ + 2H₂O (sulfuric acid acts as oxidant).

Why the others are wrong:

• A: AgNO₃ + NaI precipitates AgI (no oxidation); only second oxidizes I⁻.
• B: Br₂ + NaI oxidizes I⁻; ethanol/H₂SO₄/HI forms alkyl iodide (no halide oxidation).
• C: I₂ + NaBr shows no reaction (I₂ weaker oxidant than Br₂); CH₃CH₂I/NaOH/ethanol undergoes substitution (no halide oxidation).

Final answer: D