Reversible decomposition of ammonium chloride

Steps:

• Observe the forward reaction: warming NH4Cl(s) produces NH3(g) and HCl(g), indicating heat drives decomposition.
• Note the reverse: gases on cold surface reform NH4Cl(s), showing reversibility.
• Infer equilibrium: in a closed system, forward and reverse rates equalize dynamically.
• Determine thermodynamics: heat input for forward suggests endothermicity.

Why C is correct:

• Not enough information: Choices C and D are not provided, preventing evaluation.

Why the others are wrong:

• A: Dynamic equilibrium requires closed system with equal forward/reverse rates; open warming favors forward only.
• B: Reaction is endothermic (heat absorbed for decomposition), but statement lacks context for full assessment.

Final answer: Not enough information.