# How many moles of nitrogen, N_2, are there in 4.3*10^23 N_2 molecules?

Mar 14, 2016

${\text{0.71 moles N}}_{2}$

#### Explanation:

In order to figure out how many moles of nitrogen gas would contain that many molecules, you need to know how many molecules of a substance are needed in order to make one mole.

If you know how many molecules of a substance you get in one mole, you can use this as a conversion factor to help you find the answer.

The number of molecules that are needed in order to have one mole of a substance is known as Avogadro's number and is equal to $6.022 \cdot {10}^{23}$.

$\textcolor{b l u e}{| \overline{\underline{\textcolor{w h i t e}{\frac{a}{a}} \text{1 mole" = 6.022 * 10^(23)"molecules} \textcolor{w h i t e}{\frac{a}{a}} |}}} \to$ Avogadro's number

This is true regardless of the substance you're dealing with. Simply put, in order to have a mole of anything, you need to have $6.022 \cdot {10}^{23}$ pieces of that anything.

Use Avogadro's number as a conversion factor to get

4.3 * 10^(23)color(red)(cancel(color(black)("molec. N"_2))) * overbrace("1 mole N"_2/(6.022 * 10^(23)color(red)(cancel(color(black)("molec. N"_2)))))^(color(purple)("Avogadro's number")) = "0.71405 moles N"_2

Rounded to two sig figs, the number of sig figs you have for the number of molecules of nitrogen, the answer will be

${\text{no. of moles N}}_{2} = \textcolor{g r e e n}{| \overline{\underline{\textcolor{w h i t e}{\frac{a}{a}} 0.71 \textcolor{w h i t e}{\frac{a}{a}} |}}}$