Determination of molar mass using the ideal gas law

Principle

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.

Benefits

• Examination of many different gases possible
• Illustrative experimental setup

Tasks

Determine the molar masses of the gases helium, nitrogen, carbon dioxide and methane.

Learning objectives

• Molar mass and relative molar mass
• Properties of gases
• Ideal and ordinary gases
• Equations of state

Necessary accessories

• Precision balance 620g/0.001g