A gas expands from I to F along the three paths indicated in Figure P12.5. Figur

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(a) I ==> A: constant pressure process, work done = P*(v2-v1)= 8 atm*L = 810.5 J. A ==> F: constant volume process. Hence IAF: work done = 810.5J. It must be positive, since the volume increases. (b) First write pressure P as a function of volume v: P(v) = 7.0 - 1.5v Hence the work done = [integral](v: 2 to 4) Pdv = [7v -(3/4)v^2] (evaluate from 2 to 4) = (28-12) - (14-3) = 5 (atm*L) = 506.6 J (c) Similar to (a): Work done = 2 atm*L = 202.6 J A much simpler way is to consider the area underneath the curve. In this way: (a) 4*(4-2) = 8 (atm*L) (b) (4-2)*(4-1)/2 + 1*(4-2) = 3+2 = 5 (atm*L) (c) 1*(4-2) = 2 (atm*L)

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