Avogadro's Number

Part of the Stoichiometry section of Coddy's Chemistry journey. Lesson 2 of 41.

The number of particles in one mole, $6.02 \times 10^{23}$ , is Avogadro's number, N_A.

It was chosen so that 12 g of carbon-12, the atom relative atomic masses are measured against, holds one mole of atoms.

A balance reading 12.00 g of carbon-12 powder

12 g of carbon-12: one mole of atoms

Counting one particle a second, a mole would take about $2 \times 10^{16}$ years. To turn particles into moles, divide:

$n = \frac{N}{N_A}$

Challenge

One small drop of water holds $1.505 \times 10^{21}$ water molecules. How many moles $n$ of water is that?

Try it yourself

Solve for $n$

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Stoichiometry

1The Mole

4Equations and Mole Ratios

2Gases

5Limiting Reactant

3Solutions

6Practice Problems