Question

Find the work applied when:
There is 1 mol of N2, originally @ STP and heated, at constant volume, to 1000.0 K (CN2 = 29.124 J/mol.K). Then constant pressure is maintained and the volume of the gas changes, allowing it to expand by 20%.

I used w= -nR(delta T), -1 mol times 8.31451 times (1ooo- 273 K)= -6045 J
Then w= -P(deltaV)
-1 bar times -4.51 L= 451 J
Help?

Answer 1

First, at constant volume there is zero work. So the second part is where the work comes in. What is delta V. Initially the volume was 224 L (1 mol of a gas @ STP). 20% of that is 22.4 x 0.20 = approx 4.5 L but you need a more accuratey answer. What is the P
(P1/T1) = (P2/T2)
P1 = 1 atm
T1 = 273
P2 = ?
T2 = 1000 K
Solve for P2, then
work = -p*delta V and the units are L*atm. Convert to J by L*atm x 101.325 = ? Joules.
Post your work if you get stuck.