A sample of an oxide of nitrogen is found to contain 30.4% nitrogen. What is its empirical formula?

To find the empirical formula, follow these steps:

1. Assume you have 100g of the substance. This means you have 30.4g of Nitrogen (N) and 69.6g of Oxygen (O).

2. Convert the mass of each element to moles. Nitrogen's atomic mass is approximately 14g/mol and Oxygen's atomic mass is approximately 16g/mol.

   So, for Nitrogen: 30.4g / 14g/mol = 2.17 mol And for Oxygen: 69.6g / 16g/mol = 4.35 mol

3. Divide each mole quantity by the smallest number of moles calculated. In this case, 2.17 is the smallest.

   So, for Nitrogen: 2.17 mol / 2.17 = 1 And for Oxygen: 4.35 mol / 2.17 = 2

4. If necessary, multiply these numbers by integers in order to get whole numbers; it's not necessary in this case.

So, the empirical formula of the oxide of nitrogen in this case is NO2.