# Question a264c

Dec 8, 2017

$3.22 \cdot {10}^{23} \text{molecules}$. Check my work below to see how I did it!

#### Explanation:

When converting grams to molecules, you first have to convert it to moles. In order to do this, you first need to determine how many grams are in one mole of $S {O}_{2}$.

Start off by looking at your periodic table. If you don't have one on hand, ptable.com has a great interactive one you can use!

Find $S$ and $O$ on the periodic table. The number beneath the symbol is the molar mass. That tells you how many grams are in one mole of each element! In your specific case, you need to molar mass of $S {O}_{2}$.

$\textcolor{red}{S} :$ 32.06 grams/mol
$\textcolor{b l u e}{O} :$ 15.999 grams/mol

$32.06 + 2 \left(15.999\right) = 64.058 \text{ grams/mol}$

Notice that I added the molar mass of Oxygen twice. This is because you were given two molecules of Oxygen to work with (${O}_{2}$).

Now you can start converting! We need to first convert the grams of $S {O}_{2}$ to moles of $S {O}_{2}$. You can do this by dividing the given mass of your sample by the molar mass of $S {O}_{2}$.

34.3cancel("g")*(("1 mol")/("64.058 "cancel("g"))) = "0.5355 mol "SO_2

With the amount of moles of your sample in hand, we can convert that to the amount of molecules are present in the sample! We do this with Avogadro's number, a constant that allows the conversion between moles and molecules.

$\text{Avogadro's number = } 6.022 \cdot {10}^{23}$

Once again, we convert!

0.5355 cancel("mol") *((6.022*10^23)/(1 cancel("mol"))) = 3.22*10^23 " molecules of" SO_2#

There we go!