Question

Copper is one of a group of metal called the coinage metals. How many atoms of copper are in a pure copper coin weighing 12.0 g?

Answer 1

We need to (i) calculate the number of moles of `Cu`; and (ii) convert that molar quantity into a number.

Explanation:

`"Moles of copper"` `=` `(12.0*cancelg)/(63.55*cancelg*mol^-1)` `=` `0.189` `mol`.

Now in 1 mole of stuff there are `6.022xx10^23` individual items of that stuff. The mole is just a (large) number like a dozen, or a score, or a gross.

So all we have to do is to mulitply the molar amount by Avogadro's number:

`0.189` `cancel(mol)` `xx` `6.022xx10^23` `cancel(mol^-1)` `=` `??` `"copper atoms"`