Question

What law can be used to calculate the number of moles of a contained gas?

Answer 1

The Ideal Gas Law or Avagadro's Law

Explanation:

The Ideal Gas Law (PV = nRT) can be used if you have pressure, volume, and temperature. Where...
...P = Pressure in kPa
...V = Volume in `dm^3`
...n = The number of moles of gas present
...R = Universal Gas Constant ( `8.314` )
...T = The temperature in Kelvin

If you don't have those pieces of information, perhaps Avagadro's Law will take care of you. It says that 1 mole of any gas at standard temperature and pressure will occupy `22.4dm^3`. The only limitation of this is, that you have to deal with the gas at STP (standard temperature and pressure); i.e. 298K and 100kPa