Question

A sample consisting of 1.00 mol Ar is expanded isothermally at 0°C
from 22.4 dm3 to 44.8 dm3 (a) reversibly, (b) against a constant external
pressure equal to the final pressure of the gas, and (c) freely (against zero
external pressure). For the three processes calculate q, w, ΔU, and ΔH.

Answer 1

(Ans. (a) ∆U = ∆H = 0; q = 1.57KJ, w = −1.57KJ, (b) ∆U =
∆H = 0; q = 1.13KJ, w = −1.13KJ, (c) ∆U = ∆H = 0; q = 0, w =
0.)

Answer 2

à) w=-1.57kj, ∆u=0(as isothermal process) and Q= ∆u-w=0-(-1.57kj) =1.57kj
b) w=-1.134kj ,∆u =0and q=1.134kj
c) w=0(as pext. =0) so p*∆v=0=w
∆u=0and q=0