Which of the following is true for all reversible exothermic processes?

• A. The reaction is always non-spontaneous.
• B. The system absorbs heat from the surroundings.
• C. The enthalpy change, ΔH, is negative.
• D. The products have higher energy than the reactants.

Answer: (C)

Verified step by step guidance

1. Understand the meaning of an exothermic process: it is a process where the system releases heat to the surroundings, so the enthalpy change, \( \Delta H \), is negative.
2. Recall that \( \Delta H < 0 \) means the products have lower enthalpy (energy) than the reactants, because energy is given off during the reaction.
3. Analyze the spontaneity of the reaction: spontaneity depends on both enthalpy and entropy changes, so an exothermic process is not always spontaneous or non-spontaneous by itself.
4. Consider the heat flow: since the system releases heat, it does not absorb heat from the surroundings; rather, the surroundings gain heat.
5. Summarize that for all reversible exothermic processes, the enthalpy change \( \Delta H \) is negative, which means the products have lower energy than the reactants.