Case Study Questions
Question 1:
Read the passage given below and answer the following questions.
In chemical thermodynamics, the type of work involved is mostly pressure-volume work that is the work done when a system (gas) expands or contracts against an external opposing pressure. Hence, work is also defined as the transfer of energy that can be used to change the height of a mass in the surroundings.
Pressure-volume work: The work W, that is done due to the expansion or compression of a gas against an external opposing pressure P is called pressure-volume work
(i) Which of the following statement is correct?
(a) ΔU = Wadiabatic
(b) Wad = + ve, when work is done on the system
(c) Wad = – ve, when work is done by the system
(d) All of the above.
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Answer: d(ii) A process in which the system does not exchange heat with the surroundings is known as
(a) isothermal
(b) isobaric
(c) isochoric
(d) adiabatic.
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Answer: d(iii) Which of the following is correct match as far as the thermodynamic processes are involved?
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Answer: b(iv) 3 moles of an ideal gas are expanded isothermally and reversibly from 10 m3 to 20 m3 at 300 K. The work done is (R = 8.314 J K–1 mol–1).
(a) +5.187 kJ
(b) –5.187 kJ
(c) –2.175 kJ
(d) +3.750 kJ
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Answer: b(v) A gas expands in vacuum. The work done by the gas is
(a) zero
(b) minimum
(c) maximum
(d) cannot be predicted.
