An engine using 1 mol of an ideal gas initially at 20.7 l and 394 k performs a cycle
consisting of four steps:
1) an isothermal expansion at 394 k from
20.7 l to 40.8 l;
2) cooling at constant volume to 217 k;
3) an isothermal compression to its original
volume of 20.7 l; and
4) heating at constant volume to its original
temperature of 394 k.
find its efficiency. assume that the
heat capacity is 21 j/k and the universal gas constant is 0.08206 l atm/mol/k =
8.314 j/mol/k.
