How many moles of nitrogen, n, are in 0.286 mil of ammonium nitrate?

0.572

Explanation:

The formula for ammonium nitrate is

NH4NO3

The trick here is to realize the 4 applies only to the hydrogen. The 3 applies only to the oxygen.

There are 2 nitrogens in the formula. So if the entire molecule represents 0.286 mols. The individual mols of each part of the formula is just multiplied by the number of moles of the molecule. In formula form

Number of moles of the atoms making up the molecule = number of atoms from the formula * mols of the molecule.

2*0.286 = 0.572 moles of Nitrogen