The density of carbon dioxide at STP is 1.964 grams per liter (g/L). One mole of an ideal gas at standard temperature and pressure has the volume 22.4 liters. The mass of the ideal gas can be calculated using its molecular weight: density = molar mass/molar volume.
The molar mass of carbon dioxide is 44.01 grams. The density of carbon dioxide is 44.01/22.4, which is equal to 1.964 g/L. The values of standard temperature and pressure are 273 Kelvin and one atmosphere, respectively. If the gas is not an ideal gas, the volume of a gas at other temperatures and pressures is calculated using the Vander Waals’ equation, PV=nRT.