Moles from a Mass
To find the number of moles given a mass of a
substance you need to know its chemical formula. From
the formula you can find its molar mass. From there
this calculation is just a matter of setting up a
conversion.
You have 32.0 g of nitrogen gas in a bottle.
Nitrogen gas has the formula N_{2} and has a
molar mass of 2 x 14.00674 g/mol or 28.0135 g/mol.
1 mol
32.0 g x ------- = 1.14 mol N_{2}
28.0135 g