Question

Two identical pressure cylinders show the same pressure on the gauge. They both are at room temperature. One contains methane (CH4 ) and the other contains Nitrogen (N2 ). Use what you know about gas laws to explain how to tell which is by weighing the cylinders.

Answer 1

Because nitrogen has a larger molar mass than methane, the two substances will weigh differently even at the same pressure and temperature. The nitrogen cylinder will thus weigh more.

Step-by-step explanation:

As per the Ideal Gas Law, PV=nRT, it is assumed that both temperature (T) and pressure (P) remain constant. Since it relies on the molecular weight of the gas, the variable that will change is the mass (or weight in this instance), denoted by "n" (the number of moles). Nitrogen (N2) has a molar mass of around 28 g/mol, while methane (CH4) has a molar mass of roughly 16 g/mol. Because nitrogen molecules have a larger molar mass than methane molecules, the cylinder containing nitrogen will be heavier even if both cylinders contain the same number of molecules (because of the same pressures).