100 liters equals how many moles?
50 liters would equal how many molecules?
I don't remember this stuff

Depends on the substance.

Moles is a measure of number of molecules. Liters is a measure of what volume those molecules take up. The two are related by the molecular mass and the density of the material, so they are dependent upon the material.

For gasses there is a relationship between moles and volume, known as the ideal gas law. One mole of an ideal gas at standard temperature and pressure ("STP" = 0 degrees C, 1 atmosphere pressure) occupies 22.4 liters of volume. Thus 100 liters of an ideal gas at STP is 100/22.4 = 4.46 moles. Multiply by Avogadro's number to get the number of molecules: 4.46 moles x 6.022 x 10^23 molecules/mole = 2.69 x 10^24 molecules.

If the temp and pressure are not STP, you can use the ideal gas law to determine how many moles there are in a given volume: PV = nRT, where P=pressure(Pa), V = volume (m^3), n = number of moles, R = gas constant, and T = temp in Kelvins. The value for R depends on the units you're using - two of the most common are:

R= 8.314J/Mol K = 8.314 Pa m^3/Mol K, and
R = 0.082057 L Atm/mol K.

Ah yes of course, then it depends on temperature and pressure.

What are you looking for? :)