If you wanted to make 12 grams of copper (II) bromide, how many molecules do you need?

Avogadro's number represents the number of units in one mole of any substance. This has the value of 6.022 x 10^23 units / mole. This number can be used to convert the number of atoms or molecules into number of moles.

12 g CuBr2 (1 mol / 223.37 g) (6.022 x 10^23 molecules / mole) = 3.24x10^22 molecules CuBr2