Problem 17.23

17.23. a)
The work done by the gas is just
$W = P \Delta V$
W = (.8 atm)(- 7 L)
W = -567 J

b)
Internal energy is given by
$\Delta U = Q - W$
$\Delta U = -400 J - (-567 J)$
$\Delta U = 167 J$