Which type of energy is represented by the change in enthalpy (ΔH) in a chemical reaction?

• A. Light energy emitted during the reaction
• B. Work done by the system on the surroundings
• C. Heat energy transferred at constant pressure
• D. Electrical energy produced by the reaction

Answer: (C)

Verified step by step guidance

1. Understand that enthalpy (H) is a thermodynamic state function that represents the total heat content of a system at constant pressure.
2. Recognize that the change in enthalpy (\$\Delta H\$) during a chemical reaction corresponds to the heat absorbed or released by the system when the pressure remains constant.
3. Note that \$\Delta H > 0\$ indicates an endothermic process (heat absorbed), while \$\Delta H < 0\$ indicates an exothermic process (heat released).
4. Distinguish that \$\Delta H\$ does not represent light energy emitted, work done by the system, or electrical energy produced, but specifically the heat energy transferred at constant pressure.
5. Conclude that the type of energy represented by \$\Delta H\$ in a chemical reaction is heat energy transferred at constant pressure.