Change in enthalpy is defined as:
Correct answer: B. The total energy change at constant pressure
- A. The change in heat content
- B. The total energy change at constant pressure
- C. The heat change at constant volume if ∆n=0
- D. Work done at constant pressure
Explanation
Enthalpy change, represented by ΔH, is the total energy change in a system at constant pressure. It accounts for both heat exchange and work done by the system. Option B accurately describes this concept. Option A is incorrect because it only considers heat without accounting for pressure. Option C inaccurately describes a condition for internal energy at constant volume, not enthalpy. Option D focuses only on work, missing the heat component, hence it does not fully represent enthalpy change.
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About Thermochemistry and Energetics of Chemical Reactions
Thermochemistry measures energy changes in chemical reactions and distinguishes exothermic from endothermic processes. Work covers systems, surroundings and state functions, internal energy, the first law of thermodynamics, enthalpy and Hess's law, including the sign conventions used when heat enters or leaves a system.
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