But, Can I Use the Ideal Gas Law to Calculate the Density of Air?
This is a good question to ask, because the air in a pipe friction loss, drag force, or pitot tube calculation, is indeed a real gas, not an ideal gas. Fortunately, however, many real gases behave almost exactly like an ideal gas over a wide range of temperatures and pressures. The ideal gas law doesn’t work well for very low temperatures (approaching the critical temperature of the gas) or very high gas pressures (approaching the critical pressure of the gas). For many practical, real situations, however, the ideal gas law gives quite accurate values for the density of air (and many other gases) at different pressures and temperatures.
