Verified answer

Assume you have 100 grams of the compound. That means it has 74.1 grams of oxygen, so how many moles is that? It has 25.9 grams of nitrogen, so how many moles is that?

Your empirical formula will be the whole number ratio of the moles.

Now, lets accept your statement that the empirical formula is N2O5, which would have a mass of 108 g/mole. But the compound has a mass of 216 g/mole, so you need to double the formula.

Remember, empirical formula is the smallest ratio of the atoms, while molecular formula is the actual formula.

Suggest work in terms of 100 g.

Divide by atomic weights to obtain moles.

74.1 g / 16,0 g/mole = 4.6 moles oxygen.

25.9 g / 14.0 g/mole = 1.9 moles nitrogen.

Divide by the lower number of moles.

4.6 / 1.9 = 2.4 so O:N ratio is 2.4:1 or 5:2.

The empirical formula is N2O5.

Molar mass N2O5 = 108 g/mol.

Divide molar mass compound by RMM empirical.

216 / 108 = 2. Molecular formula = N4O10.

N2o5 Formula