Molar Mass of Gas
...he sample is first calculated using the ideal gas law, PV = nRT, where n represents the number of moles. The number of moles of a gas is found from the pressure, volume, and temperature of a sample: n = PV/RT where R is the universal gas constant. The molar mass of the gas is found from the ratio of the mass of the sample to the moles in the sample. Divide the mass of the sample by the number of moles using the value. 0.508 g = g _________ mol 1 mol In this experiment, a sample of gas is collected by water displacement. That is, the gas bubbles into a container of water and as the gas accumulates, it displaces the water. The volume of the sample is the volume the gas occupies in the container. The temperature is found by measuring the temperature of the water in contact with the gas. The mass of the gas sample is measured by weighing a small tank or cylinder of gas, delivering the sample, and reweighing the cylinder. The pressure of the sample is found by making sure that the pressure of the gas sample is the same as the atmospheric pressure. The atmospheric pressure is measured with a barometer. However, when a gas is collected by water displacement, it becomes saturated with water vapor. This means that once the gas sample is collected, it will be a mixt...