Problem 2

One mole of monatomic ideal gas starts at state

A

with

T_A=300

K and

V_A=0.010

^3

. It follows a three-step cycle: (1) heat at constant volume from

A

B

, where

T_B=600

K; (2) expand isothermally from

B

C

until the volume doubles; (3) compress at constant pressure from

C

back to

A

. Use

R=8.31

J mol

^{-1}

^{-1}

, molar

C_V=3R/2

, and define work

W

as positive when done by the gas. (a) Find the pressures at

A,B,C

. (b) Calculate work and heat for each leg. (c) Check the first law over the complete cycle.

problems.proof.stepOf

problems.proof.prevStep problems.proof.nextStep

V_C=2V_A=0.020\ \mathrm{m^3},\quad T_C=T_B=600\ \mathrm K,\quad P_C=nRT_C/V_C=P_A

problems.proof.analysis

The $BC$ leg is isothermal and ends at twice its initial volume. The state equation therefore halves the pressure, making $P_C=P_A$ as required for the isobaric return leg.