Which one of the following is the correct demonstration of first law of thermodynamics?
Correct answer: B. △E=q - P△V
- A. △H= qw
- B. △E=q - P△V
- C. △H=q+w
- D. △E = q+W
Explanation
The first law of thermodynamics states that the change in internal energy (△E) of a system is equal to the heat (q) added to the system minus the work (W) done by the system on its surroundings. The correct expression for this law is △E=q - P△V, which considers the work done during volume changes.In contrast, Option A (△H= qw) is incorrect because it does not describe the internal energy change. Option C (△H=q+w) incorrectly combines heat and work without proper context. Option D (△E = q+W) could be misleading as it doesn't specify the distinction needed for work related to volume change in certain situations.
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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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