# Question #77d78

Jan 14, 2018

$5.53$

#### Explanation:

The idea here is that in order to ahve $1$ mole of carbon dioxide, you need to have $6.022 \cdot {10}^{23}$ molecules of carbon dioxide.

So if your sample of carbon dioxide contains $6.022 \cdot {10}^{23}$ molecules of carbon dioxide, you can say that it contains $1$ mole of carbon dioxide, as stated by Avogadro's constant.

In your case, the sampel contains $3.33 \cdot {10}^{24}$ molecules of carbon dioxide, so right from the start, you know that the sample contains more than $1$ mole.

To find the number of moles present in the sample, use Avogadro's constant as conversion factor. Set it up with $1$ mole on top and $6.022 \cdot {10}^{23}$ molecules on the bottom to get

$3.33 \cdot {10}^{24} \textcolor{red}{\cancel{\textcolor{b l a c k}{{\text{molecules CO"_2))) * overbrace("1 mole CO"_2/(6.022 * 10^(23)color(red)(cancel(color(black)("molecules CO"_2)))))^(color(blue)("Avogadro's constant")) = color(darkgreen)(ul(color(black)("5.53 moles CO}}_{2}}}}$

The answer is rounded to three sig figs, the number of sig figs you have for the number of molecules of carbon dioxide present in the sample.