# 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?

Feb 3, 2016

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

#### Explanation:

$\text{Moles of copper}$ $=$ $\frac{12.0 \cdot \cancel{g}}{63.55 \cdot \cancel{g} \cdot m o {l}^{-} 1}$ $=$ $0.189$ $m o l$.

Now in 1 mole of stuff there are $6.022 \times {10}^{23}$ 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:

$0.189$ $\cancel{m o l}$ $\times$ $6.022 \times {10}^{23}$ $\cancel{m o {l}^{-} 1}$ $=$ ?? $\text{copper atoms}$