You will work with the ideal gas law and your understanding of density to apply these tools to working with molar mass problems. Now we will examine equation 1 above a bit further.
R is called the ideal gas constant.
The value of R will depend upon the units of the variables. We can use this equation just as we used equation 1 to solve problems involving changes in state variables. This EOS with density has the obvious example to how hot-air balloons work, as your text explains. Many people don't know that such balloons are totally open at the bottom of the balloon so that gas can escape from the balloon as it is heated. If we experimentally measure the density of an unknown gas at a particular T and P, then we can calculate the molecular weight of the unknown gas.