**How To Convert Atoms Or Molecules To Moles**

In order to convert atoms or molecules or formula units to moles OR to convert moles into atoms or molecules or formula units, we __must __use AVOGADRO'S number.

Avogadro's number = 6.022 *10^23 atoms or molecules or formula units per mole.

What does it mean? There are 6.022 *10^23 atoms in 1 mole. There are 6.022 *10^23 molecules in 1 mole. There are 6.022 *10^23 formula units in 1 mole.

**How to convert molecules to moles?** Divide by Avogadro's number

Let's take a look at an example:

*Convert 500 molecules of water to moles.*

We always start with what we are given:

500 molecules

Then, we put the units we want to cancel on the bottom and units we want to get on top.

500 molecules*__ moles__

molecules

Now, we must use Avogadros number. There are 6.022 *10^23 molecules in 1 mole. Whenever we use Avogadro's number we will always put 1 mole in our conversion. We get:

500 molecules* _______1____mole

6.022 *10^23 molecules

We can do the same thing for atoms and formula units.

**How to convert moles to molecules?** Multiply by Avogadro's number

Let's take a look at an example:

*Convert 4.5 moles of CH**4** to moles.*

We always start with what we are given:

4.5 moles

Then, we put the units we want to cancel on the bottom and units we want to get on top.

4.5 moles* ___________molecules

moles

Now, we must use Avogadros number. There are 6.022 *10^23 molecules in 1 mole. Whenever we use Avogadro's number we will always put 1 mole in our conversion. We get:

4.5 moles* __ 6.022 *10^23 molecules__

1 mole

Let's try a more advanced problem:

How many hydrogen atoms are in 50 moles of H2O?

We always start with what we are given:

50 moles H2O

Then, we put the units we want to cancel on the bottom and units we want to get on top.

50 moles H2O* ___________molecules

moles

Now, we must use Avogadros number. There are 6.022 *10^23 molecules in 1 mole. Whenever we use Avogadro's number we will always put 1 mole in our conversion. We get:

50 moles H2O* __6.022 *10^23 molecules of H2O__

1 mole

But we need H atoms! There are 2 hydrogen atoms in 1 H2O molecule.

50 moles H2O* __6.022 *10^23 molecules of H____2____O__ * __2H atoms__

1 mole of H2O 1 molecule H2O