Which statement about ΔH for an endothermic process is correct?

• A. Endothermic processes have ΔH > 0.
• B. Endothermic processes have ΔH < 0.
• C. Endothermic processes have ΔH = 0.
• D. Endothermic processes have ΔS > 0.

Answer: (A)

Endothermic processes involve heat flowing into the system. At constant pressure, the enthalpy change ΔH equals the heat absorbed or released (q_p). When a process takes in heat, the system’s enthalpy increases, so ΔH is positive. That’s why endothermic processes are described by ΔH > 0.

If heat were released to the surroundings, the process would be exothermic and ΔH would be negative. A zero enthalpy change would mean no heat exchange at constant pressure, which doesn’t describe an endothermic process. Entropy change (ΔS) relates to disorder and isn’t fixed by whether a process is endothermic or exothermic; endothermic reactions can have positive or negative ΔS depending on how the molecules arrange themselves.