Determination of molar mass using the ideal gas law

All gases may be considered, to a first approximation, to obey the ideal gas equation which relates the pressure p , volume V , temperature T and amount of substance n of a gas. The amount of gas n is expressed as the number of moles and is equal to m / M where m is the mass of gas present and M is the mass of one mole of the gas. The volume occupied by a known mass of gas is to be measured at a given temperature and pressure, so that the ideal gas equation can be used to estimate the molar mass of the gas.