# What is the molecular formula of a compound if its empirical formula is NO_2 and its molar mass is 138.02 g/mole?

Apr 25, 2016

138.02 g/mol $\div$ molar mass of empirical formulae = whole number,
then
Molecular Formulae = Empirical Formulae $\times$ whole number

#### Explanation:

If the molar mass of 138.02 g/mol has been provided for you,
divide it by the molar mass of $N {O}_{2}$.

Nitrogen has a molar mass of 14.0 g/mol, whereas oxygen is 16.0 g/mol
138.02 g/mol $\div$ $\left(1 \times 14.0 + 2 \times 16.0\right)$
138.02 g/mol $\div$ 46.0 g/mol = 3.00 (rounded to nearest whole number)

Since 3.00 is the whole number, multiply it by the empirical formula.

($N {O}_{2}$)$\times$3.00 = ${N}_{3} {O}_{6}$ is the molecular formula.