Question:
A sample of vitamin $\mathrm{C}$ is known to contain $2.58 \times 10^{24}$ oxygen atoms. How many moles of oxygen atoms are present in the sample?
Solution:
$6.022 \times 10^{23}$ atoms of oxygen are present $=1 \mathrm{~mol}$ atoms
$2.58 \times 10^{24}$ atoms of oxygen are present in $=\frac{(1 \mathrm{~mol} \text { atoms })}{\left(6.022 \times 10^{23}\right)} \times\left(2.58 \times 10^{24}\right)$
$=4.28 \mathrm{~mol}$ atoms $=4.28 \mathrm{~mol}$ atoms.