Work by an ideal gas in a thermodynamic cycle

[merbear]

1. Homework Statement

Two moles of an ideal gas are carried around the thermodynamic cycle shown in Fig. 18-29. The cycle consists of (1) an isothermal expansion A to B at a temperature of 700 K, with the pressure at A given by pA = 9 atm; (2) an isobaric compression B to C at PC = 4 atm; and (3) an isochoric pressure increase C A. What work is done by the gas per cycle? (See attached picture)

2. Homework Equations

pv=nRT

W=pdv

P=nRT/V


3. The Attempt at a Solution

W=nRT*ln(v2/v1)

For Pa:
9 atm= [2 mol*(.08205784 L*atm/k*mol)*700K]/V2

For Pb:

4 atm= [2 mol*(.08205784 L*atm/k*mol)*700K]/V1

V2/V1= 4/9

W=nRT(ln(4/9)) = 93.16 J (for A to B)

Here is where I got stuck. I can't seem to find the work for B to C without having variables in the answer. Once I can find the work from B to C I can add the work quantities to find the total (and ignore the value for C to B because the total work with no volume change is zero).

Any help in finding work from B to C would be appreciated.

Thank you
1. Homework Statement



2. Homework Equations



3. The Attempt at a Solution

 

[George Jones]

What is the pressure at C? What is the volume at C?

 

[bennyipfar]

You can use PV=nRT to find the volume at point A and C
Then, pluge into the formula W=nRT*ln(V2/V1)
Final subtract it with the area below that triangla W - 3*101325*(V2-V1)