4.8 Concluding Comments
Understanding how gases behave as a function of temperature and pressure is critical to understanding process operations on those gases. This will be seen further in Chapter 5, where work is performed on or performed by gases.
We have seen that the volume of gases is proportional to the number of moles and the absolute temperature of the gas, and inversely proportional to the absolute pressure. The relationship between pressure, volume, moles, and temperature when combined with the ideal gas constant gave rise to the Ideal Gas Law, permitting the calculation of any one of the four independent terms when the other three are known.
In general, most gases at less than a few atmospheres of pressure and with temperatures greater than the extreme cold of cryogenic operations (about –150°F), can be treated as ideal gases. However, when dealing with large volumes of gases as may be the case in the hydrocarbon-processing industries, even small effects caused by a nonideal gas’s behavior may have large financial consequences.