The internal energy change in the system that has absorbed 2kcal of heat and done 500J of work is:
Correct answer: C. 7900J
- A. 8900J
- B. 8800J
- C. 7900J
- D. 7500J
Explanation
According to the equation of the First Law of Thermodynamics,U = Q - WU = change in internal energyQ = heat absorbedW = work doneAlso note that 1cal = 4.2 JSo,U = (20004.2) - 500U = 8400 - 500U = 7900
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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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