Which of the following is/are the applications of first law of thermodynamics (which is also known as law of conservation of energy)?
Correct answer: C. Both A and B
- A. To study processes at constant volume (∆V = 0) only
- B. To study processes at constant pressure (∆P = 0) only
- C. Both A and B
- D. Neither A nor B
Explanation
To study processes at constant volume (∆V = 0): The first law of thermodynamics is applicable to processes that occur at constant volume. In such cases, it can be used to determine changes in internal energy (∆U) and how heat (Q) and work (W) are related. To study processes at constant pressure (∆P = 0): The first law of thermodynamics is also applicable to processes that occur at constant pressure. In this context, it can be used to analyze changes in enthalpy (∆H), where ∆H = Q (heat) at constant pressure.
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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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