Molecular formula question?

First, get the empirical formula:

4.04 g / 14.0 g/mol = 0.28857 mol

11.46 g / 16.0 g/mol = 0.71625 mol

Look for smallest whole-number ratio:

0.28857 mol / 0.28857 mol = 1

0.71625 mol / 0.28857 mol = 2.482

The smallest whole-number ratio is 2:5.

The empirical formula is N2O5

What is the weight of N2O5?

(14 x 2) + (16 x 5) = 108

108 / 108 = 1

N2O5 is also the molecular formula.

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Suppose the molecular weight was 216. We then have this:

216 / 108 = 2

N2O5 times 2 = N4O10 <--- that's the molec formula for my additional example

moles N = 4.04 g x 1 mol/14 g = 0.2886 moles

moles O = 11.46 g x 1 mol/16 g = 0.716 moles

Dividing by 0.2886 to get whole numbers, you have 1 N and 2.5

Then multiply by 2 to get 2N and 5O, so empirical is N2O5

Molec. wt of empirical is 14+14+ (5x16) = 28 + 90 = 108

So, molecular formula is N2O5