The pV-diagram in ?Fig. E20.5 shows a cycle of a heat engine that uses 0.250 mol of an ideal gas with ? = 1.40. Process ?ab is adiabatic. (a) Find the pressure of the gas at point a. (b) How much heat enters this gas per cycle, and where does it happen? (c) How much heat leaves this gas in a cycle, and where does it occur? (d) How much work does this engine do in a cycle? (e) What is the thermal efficiency of the engine?

Solution 5E Step 1: For an ideal gas undergoing adiabatic expansion or compression, we can write, PV = a constant Where, P - Pressure of the gas V - Volume of the gas - adiabatic index We know that, the ideal gas equation is, PV = nRT Where, n - Number of moles of the gas R - Universal gas constant T - Temperature of the gas