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One-quarter lbmol of oxygen gas (O2) undergoes a process from p1 = 20 lbf/in², T1 = 500oR to p2 = 150 lbf/in². For the process W = -500 Btu and Q = -127.5 Btu. Assume the oxygen behaves as an ideal gas. Determine T2, in oR, and the change in entropy, in Btu/oR.

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To determine the final temperature (T2) and change in entropy (∆S) for the given process of oxygen gas, we can use the first law of thermodynamics and the ideal gas equation. By calculating the number of moles of the gas, we can solve for T2 using the equation ∆U = Q - W = nCv(T2 - T1), and then determine ∆S using the equation ∆S = Cv ln(T2/T1) - R ln(p2/p1).

In this question, we are given information about the initial and final states of the oxygen gas and the values of work (W) and heat (Q) for the process. We are asked to determine the final temperature (T2) in oR and the change in entropy (∆S) in Btu/oR.

To solve this problem, we can use the first law of thermodynamics, which states that the change in internal energy (∆U) of a system is equal to the heat added to the system minus the work done by the system. Since the oxygen gas is behaving as an ideal gas, we can use the equation ∆U = Q - W = nCv(T2 - T1) to solve for T2, where n is the number of moles of the gas and Cv is the molar specific heat at constant volume. We can also determine ∆S by using the equation ∆S = Cv ln(T2/T1) - R ln(p2/p1), where R is the gas constant.

Given that one-quarter lbmol of oxygen gas is present, we can convert this to moles by multiplying by the conversion factor 1 lbmol/16 lb, resulting in 0.015625 moles. We can then calculate the value of T2 using the equation ∆U = Q - W = nCv(T2 - T1). Finally, we can calculate ∆S using the equation ∆S = Cv ln(T2/T1) - R ln(p2/p1).

User GlenCrawford
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Final answer:

To determine the temperature, T2, use the ideal gas law. To calculate the change in entropy, use the equation ΔS = ΔQ / T.

Step-by-step explanation:

To determine the temperature, T2, we can use the ideal gas law, which states that PV = nRT, where P is the pressure, V is the volume, n is the number of moles, R is the ideal gas constant, and T is the temperature. Rearranging the equation, we have T = PV / (nR). Given that n = 1/4 lbmol and R = 1545 ft·lbf/lbmol·°R, we can calculate T2 using the given values of p2 and V2.

To calculate the change in entropy, we can use the equation ΔS = ΔQ / T. We are given that ΔQ = -127.5 Btu and T is the average temperature during the process. We can calculate the average temperature by taking the average of T1 and T2. Plugging in the values, we can find ΔS.

User Tachyonflux
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