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2.25 moles of an ideal gas with CV, m = 3R / 2 undergoes the transformations des

ID: 2258158 • Letter: 2

Question

2.25 moles of an ideal gas with CV, m = 3R / 2 undergoes the transformations described in the following list from an initial state described by T = 310 K and P = 1.00 bar. Calculate q, w, Delta U, Delta H, and Delta S for each process. The gas is heated to 675 K at a constant external pressure of 1.00 bar. The gas is heated to 675 K at a constant volume corresponding to the initial volume. The gas undergoes a reversible isothermal expansion at 310 K until the pressure is one third of its initial value.

Explanation / Answer

(a) delta U = 2.25*3R/2 * (675-310) = 10.241 KJ

W = P*deltaV = nr*delta T = 6.87KJ

Q = U+W = 17.68KJ

(b) delta U = 10.241KJ
W = zero
Q = U+W = 10.241KJ

(c) U = zero as this is isothermal

work = Pv/3 = nr delta T /3 = 2.29

Q = 2.29