Which statement must be true for any endothermic reaction?

• A. The temperature of the surroundings increases.
• B. The reaction releases energy in the form of light.
• C. The enthalpy change, ΔH, is negative.
• D. The system absorbs heat from the surroundings.

Answer: (D)

Verified step by step guidance

1. Understand the definition of an endothermic reaction: it is a process in which the system absorbs heat from the surroundings.
2. Recall that the enthalpy change, \( \Delta H \), represents the heat absorbed or released by the system at constant pressure.
3. For an endothermic reaction, \( \Delta H \) is positive because the system gains heat, so the statement \( \Delta H < 0 \) (negative) cannot be true.
4. Since the system absorbs heat, the surroundings lose heat, which typically causes the temperature of the surroundings to decrease, not increase.
5. Therefore, the statement that must be true is that the system absorbs heat from the surroundings, consistent with the positive \( \Delta H \) and the nature of endothermic processes.