Relative ease of halide ion oxidation by sulfuric acid

Steps:

• Concentrated H₂SO₄ acts as an oxidizing agent when reacting with metal halides.
• With NaCl, HCl forms because Cl⁻ resists oxidation to Cl₂ (E° Cl₂/Cl⁻ = +1.36 V, too high for H₂SO₄).
• With NaI, I⁻ oxidizes to I₂ (E° I₂/I⁻ = +0.54 V, feasible for H₂SO₄), preventing stable HI formation.
• The key difference lies in oxidation potentials, making I⁻ easier to oxidize than Cl⁻.

Why B is correct:

• H₂SO₄ oxidizes I⁻ more readily than Cl⁻ due to the lower standard reduction potential of I₂/I⁻, explaining no Cl₂ but I₂ formation.

Why the others are wrong:

• A: Cl⁻ is harder to oxidize than I⁻, not easier.
• C: H₂SO₄ acts as an oxidizing agent here, not reducing.
• D: H₂SO₄ is not a reducing agent, and ease of reduction is irrelevant.

Final answer: B