Redox agents in disproportionation and reaction enthalpy Steps:

• ΔH = +131 kJ/mol is positive, confirming endothermic reaction.
• Reaction likely intended as Cl₂(g) + H₂O(g) → HOCl(g) + HCl(g), a disproportionation.
• Cl oxidation state: 0 in Cl₂ to +1 in HOCl (oxidized) and -1 in HCl (reduced).
• H₂O supplies oxygen to oxidize part of Cl₂, making H₂O oxidizing agent and Cl₂ reducing agent.

Why C is correct:

• Endothermic per positive ΔH; H₂O oxidizes Cl (0 to +1) by providing electronegative oxygen, per redox definition where oxidizing agent causes oxidation.

Why the others are wrong:

• A: Wrongly assigns Cl₂ as oxidizing agent (it's partially oxidized) and H₂O as reducing.
• B: Misidentifies agents and claims exothermic (ΔH > 0).
• D: Misidentifies agents and claims exothermic (ΔH > 0).

Final answer: C