What will be the change in internal energy when work done by the system is 50 kJ and heat absorbed is 140 kJ?
Correct answer: D. 90 kJ
- A. -190 kJ
- B. 190 kJ
- C. -90 kJ
- D. 90 kJ
Explanation
According to the first law of thermodynamics, if a system absorbs 140 kJ of heat energy (Q) and uses 50 kJ to do work (W) on its surroundings, its internal energy would increase by 90 kJ.Mathematically,∆Q = ∆W + ∆U140 kJ = 50 kJ + ∆U∆U = (140 - 50) kJ∆U = 90 kJConventionally, heat absorbed, work done by the system on surroundings, and increase in internal energy are all taken as positive.
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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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