Reactions of Hydrogen Bromide Steps:

• Recall that concentrated H2SO4 reacts differently with HCl versus HBr due to reducing strength.
• Check thermal stability: bond dissociation energy decreases from HCl to HBr, affecting decomposition temperatures.
• Identify precipitate color from AgNO3 reaction with HBr gas, forming AgBr.
• Examine redox potential between I2 and HBr to predict color change in solution.

Why A is correct:

• HBr reduces concentrated H2SO4 because Br⁻ is a stronger reducing agent than Cl⁻; reaction: H₂SO₄ + 2HBr → SO₂ + Br₂ + 2H₂O, producing SO₂ gas.

Why the others are wrong:

• B: HBr decomposes at lower temperature than HCl due to weaker H-Br bond (324 kJ/mol) versus H-Cl (431 kJ/mol).
• C: AgBr precipitate is pale yellow or cream, not distinctly yellow as stated.
• D: No reaction occurs; I₂ cannot oxidize Br⁻ to Br₂ (E° Br₂/Br⁻ > E° I₂/I⁻), so solution stays colored.

Final answer: A