Question

One mole of an ideal gas with CV,m = 5/2R undergoes the transformations described in the following list from an initial state described by T = 250 K and P = 1.00 bar. Calculate q, w, ΔU, ΔH, and ΔS for each process. b. The gas undergoes an adiabatic expansion against a constant external pressure of 0.500 bar until the final pressure is half its initial value. My teacher used b) q = 0 (adiabatic) nCv,m (Tf-Ti) = -Pexternal [(Vf)-(Vi)] Tf = 279 K ΔU = w = -965 J ΔH = -1.35 x 103 J ΔS = -nR ln (Pf/Pi) + nCp,m ln (Tf/Ti) = 1.28 J/K. Can someone explain how they got nRPexternal(tf/pf - Ti/Pi)?

          One mole of an ideal gas with CV,m = 5/2R undergoes the transformations described in the following list from an initial state described by T = 250 K and P = 1.00 bar. Calculate q, w, ΔU, ΔH, and ΔS for each process.

b. The gas undergoes an adiabatic expansion against a constant external pressure of 0.500 bar until the final pressure is half its initial value.

My teacher used b) q = 0 (adiabatic) nCv,m (Tf-Ti) = -Pexternal [(Vf)-(Vi)] Tf = 279 K ΔU = w = -965 J ΔH = -1.35 x 103 J ΔS = -nR ln (Pf/Pi) + nCp,m ln (Tf/Ti) = 1.28 J/K. Can someone explain how they got nRPexternal(tf/pf - Ti/Pi)?

Added by Caroline A.

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