How do you determine the density of a gas?
One way to measure the density of a gas is to take a given volume of the gas and determine its mass.
For example, you could fill a syringe of known mass and volume with the gas and measure the mass of the gas.
A syringe with a mass of 45.861 g is filled with 50.0 mL of carbon dioxide at the lab temperature and pressure (1.00 atm and 20 °C). If the empty syringe has a mass of 45.953 g, what is the density in grams per litre of the CO₂ under laboratory conditions?
Mass of CO₂ = (45.953 – 45.861) g = 0.092 g