An ideal gas is expanded isothermally and reversibly at 0 C from 1 to 1/10 bar.

Question

An ideal gas is expanded isothermally and reversibly at
0 C from 1 to 1/10 bar. Calculate (a) w per mole, (b ) q per mole,
( c) change in molar enthalpy , (d ) change in molar Gibbs free energy , and (e ) change in molar entropy for the gas.
For the second process, initial temperature and final temperature are at 273K. One mole of an ideal gas in 22.71 L is allowed to expand irreversibly into an evacuated vessel such that the ?nal total volume is 227.1 L. Calculate (f) w per mole, (g) q per mole, (h) change in molar enthalpy , (i) chane in molar Gibbs free enrgy , and (j) change in molar entropy for the gas. Calculate (k) change in molar entropy for the system and its surroundings involved in the reversible isothermal expansion and calculate (l) change in molar entropy for the system and its surroundings involved in an irriversible isothermal expansion in which the gas expands into an evacuated vessel such that the final total volume is 277.1L.

Explanation / Answer

REFER:(http://answers.yahoo.com/question/index?qid=20090408093813AAvpK9A)

PART 1
For an isothermal process,

PV=constant

(1)(V1)=(1/10)(V2)

V2=10(V1)

(a)W= (nRT)X [ln(V2/V1)]

W per mole =RTX [ln(V2/V1)]

= 8.314X 273X ln(10)

= 5.2 KJ

(b)isothermal process, change in internal energy is 0 as temperature remains constant

therefore, q=-W

q per mole=-W per mole=-5.2 KJ

(c)enthalpy change(dH)=0

(d) change in molar gibbs free energy=?G = -n*R*T*ln(V2/V1)

= -5.2 KJ

(e) dS= q/T=R*ln(v2/v1)=19.04 J/T

PART 2:

in this case P1=10XP2

proceed as in part 1 except that the process is irreversible

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