The energy absorbed as heat by an ideal gas for an isothermal process is equal to:
Correct answer: A. The work done by the gas
- A. The work done by the gas
- B. The work done on the gas.
- C. Change in the internal energy of the gas
- D. Zero, since the process is isothermal
Explanation
During an isothermal process, temperature and internal energy remain unchanged. The first law of thermodynamics states that internal energy = heat transferred + work done. Heat absorbed is considered positive (what is happening here); heat loss is negative. Work done on gas is positive; work done by gas is negative.So when we put values in the equation0 = +heat transfer +work doneheat transfer = - work doneSince work done is negative, work is done by the gas which is option A.
This question appeared on the ETEA MDCAT 2015 paper, which you can sit online with every answer explained.
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About First Law of Thermodynamics
The first law relates heat supplied, work done and the change in internal energy through energy conservation. Problems use sign conventions and apply the law to isothermal, adiabatic, isobaric and isochoric processes. Internal energy is a state function, while heat and work depend on the path followed.
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