What is the density of CH₄ at 25 °C and 1 atm? How about Xe?

Find the mass of CH₄ in 1 cm³

That is, find the mass and the volume of 1 mole of CH₄ and you will have found its density!

So, what is the volume that 1 mole of methane occupies?

V = 24.47 L

density equals mass divided by volume...

1 mole of Xe will occupy the same volume as 1 mole of methane; after all, the ideal gas law does not have a term (variable) for kind of gas, just amount of gas!

so, the density of Xe is

A simple experiment can be performed to determine the molar mass of an unknown volatile liquid. 1.5021 g of a volatile liquid was placed in a container which had a small pin-hole in the top, and the container was placed in boiling water. After all of the liquid had vaporized and the vapor stopped escaping from the pin-hole the container was cooled back to room temperature. 0.7523 g of the volatile liquid remained in the container, the volume of the container is 0.500 L, and the atmospheric pressure on that day was 756 torr. Determine the molar mass of this compound.

To determine the molar mass the number of moles in a given mass needs to be determined.

So, the question we have to answer is how many moles of liquid are present in a sample of liquid.

The key here is that at one point in the experiment all of the liquid was converted to gas.

"After all of the liquid had vaporized the container was cooled back to room temperature. 0.7523 g of the volatile liquid remained in the container"

So, we have alot of information about the unknown.

We know

• The mass of the unknown gas in the container is 0.7523 g.
  After all the liquid was converted to vapor the container was cooled and the vapor which was in the container condensed to a liquid. The mass of the liquid can be determined by weighing it on a balance.
  
• The volume that the gas occupies is 0.500 L
  As the liquid vaporizes it pushes the air out of the container. When all the liquid has vaporized only the unknown vapor is in the container. The volume of the container is 0.500 L.
  
• The pressure of the gas is 756 torr or 0.9947 atm.
  Since there is a pinhole in the container the gas on the inside of the container is at the same pressure as the gas outside the container. The gas outside the container is the atmosphere, and the pressure of the atmosphere was 756 torr.
  
• The temperature of the gas is 100 °C, or 373.15 K.
  While the container was place in boiling water the vaporized unknown filled the container. So, the temperature of the gas was the same as the temperature of the boiling water.

So,

We know P, V, and T! We can find n.

n = 0.016242 mol

So, g per mole