# The molar mass of NO_2 is 46.01 g/mol. How many moles of NO_2 are present in 114.95 g?

Jan 10, 2016

$\text{2.498}$

#### Explanation:

A substance's molar mass tells you the mass of one mole of that substance.

In your case, nitrogen dioxide, ${\text{NO}}_{2}$, is said to have a molar mass of $\text{46.01 g/mol}$. That means that every mole of nitrogen dioxide will have a mass of $\text{46.01 g}$.

So, in essence, molar mass is simply a conversion factor between number of molecules and mass.

Since you need $\text{46.01 g}$ of nitrogen dioxide in order to have one mole of the compound, it follows that $\text{114.95 g}$ will contain

114.95 color(red)(cancel(color(black)("g"))) * "1 mole NO"_2/(46.01color(red)(cancel(color(black)("g")))) = "2.49837 moles NO"_2

Rounded to four sig figs, the number of sig figs you have for the molar mass of the compound, the answer will be

${n}_{N {O}_{2}} = \textcolor{g r e e n}{\text{2.498 moles}}$