Question

What is meant by the `"mole"`? How is it useful in chemical calculations?

Answer 1

If I have a mole of stuff, there are `6.022xx10^23` individual items of that stuff.

Explanation:

So if you have a dozen eggs, there are `(12*eggs)/(6.022xx10^23*eggs*mol^-1)`. Now obviously this is a ridiculously small number, and of no use to any calculation.

However, if I have gram quantities of elements or compounds, this is a useful exercise, because in `12.00*g` `""^12C` there are `6.022xx10^23` `""^12C` atoms, `"1 mole"` of `""^12C` atoms. I could repeat these elemental molar masses for every element in the Periodic Table, and you will always have access to one of these in every test in Chemistry and Physics you ever sit.

So given a molar mass and an actual mass of stuff, elements or compounds, you know precisely how many individual atoms and molecules you have. I would try to get my head round this, because the concept is fundamental to chemistry.