# Why is "Avogadro's number" used to count atoms and molecules?

Mar 16, 2017

Why is the $\text{dozen}$ a convenient unit to count eggses?

#### Explanation:

$\text{One mole}$ specifies $\text{Avogadro's number of particles}$. ${\text{Avogadro's number of }}^{12} C$ atoms has a mass of $12.00 \cdot g$ precisely. And thus if I know the mass of a reactant in a chemical reaction, I know reasonably precisely how many reactant particles there are, how many coreactant particles it will react with, and how many product particles I should expect to get after reaction.

There should be many older answers that deal with these sorts of problems. Here is a start with some other links. The lesson that your teacher wants you to learn is that the mole is the link between the micro world of atoms and molecules, with the macro world of grams and litres.