Question

One mole of an ideal monatomic gas initially at 300 K is expanded from an initial pressure of
10 atm to a final pressure of 1 atm. Calculate ��E, q, w, ��H, and the final temperature T2 for
this expansion carried out according to each of the following paths. The molar heat capacity
at constant volume for a monatomic gas is CV = 3/2 nR. Taken from Tinoco 2.8.
(a) An isothermal, reversible expansion.
(b) An expansion against a constant external pressure of 1 atm in a thermally isolated
(adiabatic) system.
Hint for part b: The transition is not isothermal. Be patient and write down everything you
know. You will find that ��E = -1.35 x 103 J.
(c) An expansion against zero external pressure (against a vacuum) in an adiabatic system.

Answer 1

a)
dU = 0 J
dH = 0 J
w = -5743.11 J
q = 5732.11 J

b)
q = 0 J
dU = -1350 J
w = -1350 J
V2 = 15.78 L
T2 = 192.3 K
dH = -2238.55 J