Equip your students with the tools to dig themselves out of any difficulties with moles and Avogadro’s number

In chemistry, a **mole** is a **really big number**. This number (**6.02 x 10 ^{23}**) comes from the number of atoms in

**12 g of carbon-12**(this is the carbon isotope with six protons and six neutrons).

So, we can say that one **mole** of protons has a mass of one gram, and one **mole** of neutrons has a mass of one gram, as protons and neutrons have similar masses.

This means that:

- One
**mole**of^{1}H atoms has a mass of one g. - One
**mole**of^{19}F atoms has a mass of 19 g, and two moles have a mass of 38 g. - One
**mole**of NH_{3}molecules – which has a relative molecular mass (*Mr*) of 17 – has a mass of 17 g, and half a**mole**has a mass of 8.5 g. - One
**mole**of ibuprofen (C_{13}H_{18}O_{2}) has a mass of 206 g, and 0.01**moles**have a mass of 2.06 g (which is still way more than is in an ibuprofen tablet).

**Moles** allow us to compare the number of atoms or molecules in two or more different substances without writing out long numbers.

## Download this

Infographic poster, fact sheet, worksheet and teacher notes. Display the poster in your classroom or on a projector. Alternatively, print it and use it as a handout.

Use the accompanying fact sheet and worksheet to get your students to apply their mathematical skills to three different types of problems involving moles.

## Calculating moles

The relationship between moles (mol), mass (g) and *Mr* (g mol^{-1}) can be represented by this equation:

### Did you know …?

The average furry European mole is approximately 100 g. So, a **mole** of furry European moles would have a mass of: 6.02 x 10^{22} kg. Similar to the mass of the Moon at 7.35 x 10^{22} kg. That is one huge ball of fur.

## Avogadro’s constant

Remember that we said a **mole** is a **really big number**…

We can use Avogadro’s constant to calculate the number of atoms or molecules from the number of moles or vice versa, using the following relationship:

**Did you know…?**

**Amedeo Avogadro** didn’t calculate the value of the **mole**, but he was the first to claim that different gases at the same volume and pressure would contain the same number of particles. Sadly, he died before anyone figured out the number that bears his name.

## More resources

- Use the ideas in these five steps to help learners master mole calculations.
- Quiz 16–18 learners on the mole, moles and mass and other chemistry methods with these quantitative chemistry questions.
- Practise more mathematical competencies with these Starter for 10 questions for learners transitioning to post-16 study.
- Attend our teacher suppport session to learn more about teaching moles.

### Downloads

#### Introducing moles and Avogadro's number poster

**Handout**| PDF, Size 0.78 mb#### Introducing moles and Avogadro's number poster_white

**Handout**| PDF, Size 0.81 mb#### Moles calculations student sheet

**Handout**| PDF, Size 0.25 mb#### Moles calculations teacher notes

**Handout**| PDF, Size 0.23 mb#### Moles calculations student sheet

**Editable handout**| Word, Size 0.46 mb#### Moles calculations teacher notes

**Editable handout**| Word, Size 0.45 mb#### Introducing moles and Avogadro's number fact sheet

**Editable handout**| Word, Size 0.45 mb#### Introducing moles and Avogadro's number fact sheet

**Handout**| PDF, Size 0.17 mb

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