. We can next calculate DSsur from the heat
that is taken up from the environment: 
.
Finally the free energy change for an increase in volume at constant temperature in an
ideal gas can be determined as: First calculate the heat and work. Since this is an isothermal ideal gas, the change in internal energy is zero and q = -w. w = -Pex
DV = -(1 mole)(1 atm)(9 liters)(101 J/(atm l)) = -909 J. Thus q is 909 Joules. Now we can do the calculations:We calculate the DSsys
from the amount of heat that would be transferred if the process had gone reversibly: . We can next calculate DSsur from the heat
that is taken up from the environment: .
Finally the free energy change for an increase in volume at constant temperature in an
ideal gas can be determined as:
