The ratio of the mass of O to the mass of N in N2O3 is 12:7. Another binary compound of nitrogen has a ratio of O to N of 16:7.

What is its formula?

Express your answer as a chemical formula.

NO2

Explanation:

Molar mass of Nitrogen (N) is 14g / mole. Molar mass of O is 16g / mol. So the ratio of atoms of each is:

Moles of O = mass of O / Molar mass O = 12 / 16 = 0.75 = 3/4 mole of O

Moles of N = mass of N / Molar mass N = 7 / 14 = 0.5 = 1/2 mole of N

So to scale these fractions to a whole number, multiply both by 4.

4 x 3/4 = 3 moles of O; 4 x 1/2 = 2 moles of N. This confirms your first answer: N2O3.

Do the same for the ratio 16:7.

Moles O: 16 / 16 = 1 mole of O

Moles of N: 7 / 14 = 1/2 mole of N

This means for each 1/2 mole of N we have 1 mole of O; or for each mole of N we have 2 moles of O : the ratio is 2.

Multiplying both by 2: N = 1 mole; O = 2 moles. So the molecule is NO2.