22. The First Law of Thermodynamics

(I) One liter of air is cooled at constant pressure until its volume is halved, and then it is allowed to expand isothermally back to its original volume. Draw the process on a PV diagram.

(II) Sketch a PV diagram of the following process: 2.5 L of ideal gas at atmospheric pressure is cooled at constant pressure to a volume of 1.0 L, and then expanded isothermally back to 2.5 L, after which the pressure is increased at constant volume until the original pressure is reached.

(II) A 1.0-L volume of air initially at 3.5 atm of (gauge)pressure is allowed to expand isothermally until the (gauge) pressure is 1.0 atm. It is then compressed at constant pressure to its initial volume, and lastly is brought back to its original pressure by heating at constant volume.

(b) How much work does the 1.0 L of air do in this process?

(III) In the process of taking a gas from state a to state c along the curved path shown in Fig. 19–33, 85 J of heat leaves the system and 55 J of work is done on the system. (a) Determine the change in internal energy, Eᵢₙₜ, ₐ - Eᵢₙₜ, 𝒸 .

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(III) In the process of taking a gas from state a to state c along the curved path shown in Fig. 19–33, 85 J of heat leaves the system and 55 J of work is done on the system. (b) When the gas is taken along the path cda, the work done by the gas is W = 38 J. How much heat Q is added to the gas in the process cda?

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(III) In the process of taking a gas from state a to state c along the curved path shown in Fig. 19–33, 85 J of heat leaves the system and 55 J of work is done on the system. (c) If Pₐ = 2.2 P𝒹, how much work is done by the gas in the process abc?

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(III) In the process of taking a gas from state a to state c along the curved path shown in Fig. 19–33, 85 J of heat leaves the system and 55 J of work is done on the system. (d) What is Q for path abc?

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(III) In the process of taking a gas from state a to state c along the curved path shown in Fig. 19–33, 85 J of heat leaves the system and 55 J of work is done on the system. (e) If Eᵢₙₜ, ₐ - Eᵢₙₜ, _b = 15 J , what is Q for the process bc?

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