# What is the definition of a mole?

Dec 2, 2016

A mole is simply a another collective number, like a dozen, a Baker's dozen, or a gross, or ...........?

#### Explanation:

Admittedly, $\text{the mole}$ is a very large number.

One mole of stuff $\equiv$ $6.022140857 \left(74\right) \times {10}^{23}$ individual items of that stuff. Why should we use such an absurdly large number?

It turns out that if we have $6.0221 \times {10}^{23}$ individual ""^1H atoms, i.e. $\text{a mole}$ of ""^1H atoms, we have a mass of $1 \cdot g$ precisely. The mole is thus the link between the micro world of atoms and molecules, which we can't see, but whose chemistry we can observe, with the macro world of grams, and kilograms, and litres, which we can measure by suitable means in a laboratory.

The molar mass of any individual element is quoted on the Periodic Table. This is a basic, foundational principle of chemistry, and it would be worth your while to get your head round it. And this leads on to the principle of $\text{chemical equivalence}$, where a $\text{mass}$ represents a given number of molecules, or atoms, or particles. And thus a mass of substance can represent a specific number of particles.