Constant Temperature process

Let us refer to figure 7.4

Figure 7.4

The system is allowed to undergo an expansion process while in contact with constant temperature bath. During the expansion process, the opposing force is continuously reduced. System is in equilibrium at all times. Applying the first law, one can write

(7.12)

For an ideal gas, the desired property relations are

and

(7.13)

Since the temperature is held constant, du=0 and Q=W . We can also write

(7.14)