Question

How many atoms are in in 13.2 mol copper?

Answer 1

`13.2xxN_A" copper atoms"`, where `N_A="Avogadro's number"`.

Explanation:

`N_A="Avogadro's number"=6.022140857(74)xx10^23*mol^-1`.

I may use `N_A` as I would use any other collective number: `"dozens, Bakers' dozens, scores, gross, etc."` Of course, `N_A` is an unfeasibly large number, and it happens that `N_A` `""^1H" atoms"` have a mass of precisely `1*g`. `N_A` is thus the link between the sub-micro world of atoms, and molecules, that which we can conceive of, and theorize about, and the macro world of `"grams"`, and `"litres"`, and `"kilograms"`, that which we measure in a lab.

In an exam, would you have to remember `N_A`? The answer is no, as it will quoted to you as supplementary material. You do have to be able to manipulate it, and to demonstrate its significance.