Question

A sample of fuel is found to contain 87.4% nitrogen and 12.6% hydrogen. if the molecular mass of the fuel is 32.05 grams/miles, what is the molecular formula of the fuel?

Answer 1

We find the number of moles by weight percentage:

The number of moles of Nitrogen = 87.4 g/ 14.0067 g/mol = 6.24 moles
Similarly, the number of moles of Hydrogen = 12.6 g / 1.008 g/mol = 12.5 moles

Now, we divide the no of moles to get a ratio : 12.5 / 6.24 = 2

Thus, the empirical formula from this ratio will be NH2 ( molar mass = 16.02 g/mol)

32.05/ 16.02 = 2

Thus, given mass of fuel is 32.05, so its empirical formula will be N2H4