During the compression of a gas inside a cylinder, the required work input is 7000 kJ, while a heat interaction of 3000 kJ is rejected to heat the surroundings. What is the internal energy change of the gas__________________ kJ?
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Answer: A. +4000
Explanation
The first law of thermodynamics relates internal energy change to heat added and work done. Work input during compression represents energy added to the system, making it negative thermodynamically. Subtracting the rejected heat from the compression work yields a positive internal energy change. The governing thermodynamic equation states that change in internal energy equals heat minus work. Energy conservation principles dictate that work input increases gas temperature and internal energy storage. Standard sign conventions treat heat rejected from a system as a negative energy quantity.
Compressing industrial gases requires accurate internal energy calculations to prevent equipment overheating and failure. Thermodynamic modeling of compressors helps engineers optimize energy efficiency in chemical manufacturing plants. Pneumatic systems rely on these exact energy balances to predict operating temperatures during rapid compression cycles. Option B incorrectly applies sign conventions, reversing the proper direction of the internal energy change. Option C incorrectly adds the absolute values together instead of properly applying the energy balance. Option D incorrectly assumes a large negative internal energy drop despite continuous mechanical work input.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
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