Question

An unknown gas with a mass of 205 g occupies a volume of 20.0 L at 273 K and 1.00 atm. What is the molar mass of this compound?

Answer 1

The molar mass of this compound is 0.004 m/g

Firstly, molar mass is moles/grams so we need to solve for the number of moles and we were already given the grams (205 g).

So to solve for moles we were given 205 g, 20.0 L, 273 K and 1.00 atm. Knowing these numbers we can plug them into the ideal gas law, PV=nRT

where P is pressure, V is volume, n is number of moles, R is the gas constant (in this case it is 0.08206) and T is the temperature.

`PV=nRT\\\\n=(PV)/(RT)\\\\n=(1.00*20.0)/(0.08206*273) =0.893`

Next, we use moles and grams to solve for molar mass:

`(0.893)/(205) =0.004`