Lab: Determination of molar mass using the gas law

Principles and objectives:

All gases can be considered, as a first approximation, to obey the ideal gas equation which relates the pressure P, volume V, temperature T, and the amount of substance n of a gas expressed in number of moles. This number is equal to m / M where m is the mass of the gas present and M is the mass of one mole of gas. The volume occupied by a known mass of gas must 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.

Experiments aim to determine the molar masses of the gases helium, nitrogen, carbon dioxide, and methane.

- Tripod / Stainless steel rods / Universal clamp / Double nut - Syringe holder with stopper / 100 mL syringe - 3-way valve / Glass ball 2 valves, 100 mL / 500 mL safety bottle, glass - Pressure gauge, 0..-1000 mbar - Bent glass tubes / 3-way T valve - Two-stage vane vacuum pump, 115 / 230 V / Vacuum pump connector - Rubber hose for vacuum experiments, i.d. = 6mm + i.d. = 8mm / Clamps - Digital LCD display weather station - Silicone grease, 50 g / Compressed gas regulator - Gas in cylinders, N2, 12 L / CO2, 21g / Methane, 12 L / He, 12 L Accessory required: 1mg precision balance