# What is the numerical setup for calculating the number of moles of CO_2 present in 11 grams of CO_2?

Jan 1, 2017

#### Answer:

Here's how to get the numerical setup.

#### Explanation:

You must use the molar mass of ${\text{CO}}_{2}$ as a conversion factor to convert grams of ${\text{CO}}_{2}$ to moles of ${\text{CO}}_{2}$.

The molar mass of ${\text{CO}}_{2}$ is 44.01 g/mol.

Thus, the conversion is either (a) $\left({\text{44.01 g CO"_2)/("1 mol CO}}_{2}\right)$ or (b) $\left({\text{1 mol CO"_2)/("44.01 g CO}}_{2}\right)$.

You want an equation like

${\text{11 g CO"_2 × "conversion factor" = "? mol CO}}_{2}$

The conversion factor must have the desired units of your answer (${\text{mol CO}}_{2}$) on top, so you choose option (b).

The numerical setup is

11 color(red)(cancel(color(black)("g CO"_2))) × ("1 mol CO"_2)/(44.01 color(red)(cancel(color(black)("g CO"_2))))= "0.25 mol CO"_2

Note that the units of "${\text{g CO}}_{2}$" cancel and give you the correct units for the answer.