# Howe would you calculate the number of moles of Cl atoms in 3.61x10^24 formula units of magnesium chloride, MgCl_2?

Mar 26, 2017

Use Avogadro’s number to calculate the number of moles of $M g C {l}_{2}$. The number of moles of Cl is twice as much, because the ratio of Cl in $M g C {l}_{2}$ to $M g C {l}_{2}$ is 2:1.

$\frac{3.61 \cdot {10}^{24}}{6.022 \cdot {10}^{23}} = 5.99$
Therefore, there are 12 moles of Cl.

Mar 26, 2017

There are $7.22 \times {10}^{24}$ atoms $\text{Cl}$ in $3.61 \times {10}^{24}$ formula units of $\text{MgCl"_2}$.

#### Explanation:

Each formula unit of magnesium chloride, $\text{MgCl"_2}$, contains two chlorine, $\text{Cl}$, atoms.

Multiply the number of formula units by the conversion factor

(2color(white)(.)"atoms Cl")/(1color(white)(.)"formula unit MgCl"_2.

3.61xx10^24color(red)cancel(color(black)("formula units MgCl"_2))xx(2color(white)(.)"atoms Cl")/(1color(red)cancel(color(black)("formula units MgCl"_2)))=7.22xx10^24"Cl atoms"