In an endothermic process, the change in enthalpy is

In an endothermic process, the change in enthalpy is

• A. Positive.
• B. Negative.
• C. Zero.
• D. Undefined.

Answer: (A)

In an endothermic process, the system absorbs heat from its surroundings, so the heat content of the system increases. Enthalpy change (ΔH) at constant pressure equals the heat exchanged, and since heat flows into the system, ΔH is positive. A positive ΔH reflects the added energy stored as enthalpy. By contrast, if heat were released to the surroundings, ΔH would be negative (exothermic). A zero ΔH would imply no net heat transfer, which doesn’t describe an endothermic process, and undefined would suggest the states aren’t clearly defined—enthalpy is a state function, so it is defined for a transition between two states.

In an endothermic process, the system absorbs heat from its surroundings, so the heat content of the system increases. Enthalpy change (ΔH) at constant pressure equals the heat exchanged, and since heat flows into the system, ΔH is positive. A positive ΔH reflects the added energy stored as enthalpy. By contrast, if heat were released to the surroundings, ΔH would be negative (exothermic). A zero ΔH would imply no net heat transfer, which doesn’t describe an endothermic process, and undefined would suggest the states aren’t clearly defined—enthalpy is a state function, so it is defined for a transition between two states.