A system absorbs 100 kJ of heat and performs 50 kJ of work on the surroundings. The change in internal energy of the system is:
Correct answer: A. 50 kJ
- A. 50 kJ
- B. 100 kJ
- C. 150 kJ
- D. 5000 kJ
Explanation
According to the first law of thermodynamics, ΔU = q + w. Heat absorbed is positive (q = +100 kJ), and work done by the system is negative (w = -50 kJ). Therefore, ΔU = 100 kJ - 50 kJ = 50 kJ.
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About Internal Energy
Internal energy is the total microscopic kinetic and potential energy of a system and is a state function. The first law, ΔU = q + w, connects changes in internal energy with heat and work, including sign conventions, expansion or compression and constant-volume processes.
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