Accurate halogen reaction statement

Steps:

• Review halogen trends: oxidizing power and volatility decrease down the group due to increasing atomic size.
• Assess iodine's role: it accepts electrons as an oxidizing agent.
• Examine H2-Cl2 reaction: equimolar explosion yields single product via chain mechanism.
• Analyze NaBr-H2SO4 reaction: bromide reduces sulfuric acid to SO2 and bromine.

Why C is correct:

• Equimolar H2 + Cl2 explodes to form only HCl (H2 + Cl2 → 2HCl), as the chain reaction (initiation, propagation, termination) produces no byproducts.

Why the others are wrong:

• A: Iodine acts as an oxidizing agent (I2 + 2e⁻ → 2I⁻).
• B: Volatility decreases from Cl to I due to stronger van der Waals forces from larger size.
• D: Products are Br2 and SO2 (2NaBr + 3H2SO4 → 2NaHSO4 + Br2 + SO2 + 2H2O), not H2S.

Final answer: C