6.1 Avogadro's Number and the Mole
Notes
A mole (mol) is a counting unit for tiny particles, like a dozen means 12.
- 1 mol $= 6.02 \times 10^{23}$ particles. This is Avogadro's number, $N_A$.
- "Particles" can be atoms, molecules, ions or formula units, depending on the substance.
- Moles to particles: multiply by $6.02 \times 10^{23}$. Particles to moles: divide by $6.02 \times 10^{23}$.
- Example: 1.50 mol Fe $\times\ 6.02 \times 10^{23} = 9.03 \times 10^{23}$ atoms.
Practice
How many molecules are in 3.00 mol of water?
$3.00 \times 6.02 \times 10^{23} = 1.806 \times 10^{24} \approx 1.81 \times 10^{24}$ molecules.
How many moles is $3.01 \times 10^{24}$ atoms of carbon?
$\displaystyle \frac{3.01 \times 10^{24}}{6.02 \times 10^{23}} = 5.00$ mol.
Which sample contains the most atoms?
Each mole of any element has the same number of atoms, so the largest number of moles wins.
Ready for more? Take the Unit 6 test.