Consider a heat engine that is not reversible. The engine uses 1.000 mol of a diatomic ideal gas. In the first step (A) there is a constant temperature expansion while in contact with a warm reservoir at 373 K from P1 = 1.55 × 105 Pa and V1 = 2.00 × 10−2 m3 to P2 = 1.24 × 105 Pa and V2 = 2.50 × 10−2 m3 . Then (B) a heat reservoir at the cooler temperature of 273 K is used to cool the gas at constant volume to 273 K from P2 to P3 = 0.91 × 105 Pa. This is followed by (C) a constant temperature compression while still in contact with the cold reservoir at 273 K from P3 , V2 to P4 = 1.01 × 105 Pa, V1 . The final step (D) is heating the gas at constant volume from 273 K to 373 K by being in contact with the warm reservoir again, to return from P4, V1 to P1, V1.
(a) Find the change in entropy of the cold reservoir in step B. Remember that the gas is always in contact with the cold reservoir.
(b) What is the change in entropy of the hot reservoir in step D?
(c) Using this information, find the change in entropy of the total system of gas plus reservoirs during the whole cycle.