Question

What is a `"mole"`?

Answer 1

The mole is simply a number such as a `"dozen"`, or a `"Bakers' dozen"`, or a `"Botany Bay dozen"`...............

Explanation:

Of course, the mole is an exceedingly large number, i.e. `6.022.....xx10^23*mol^-1`. Why should we use it? Well if I have `6.022xx10^23` `""^1H` atoms, I have a mass of `1.0*g` precisely; or if I have `6.022xx10^23` `""^12C` atoms, I have a mass of `12.0*g` precisely. It is thus the link between the submicro world of atoms and molecules to the macro world of grams, and kilograms, and litres - that which we can weigh out on a balance, or can measure in a beaker. So can you tell me the MASS of `1*mol` of `""^12CH_4` molecules?

The use of the mole allows us to establish chemical equivalence by means of mass, and (sometimes) by volume. If I have a mass of something of known formula, I know precisely the number of molecules or atoms that constitute that mass. And thus I can establish stoichiometric equivalence by means of mass or volume.

This principle is basic to the study of the chemistry, and is worth spending some time on in order to get it right.