The formula units corresponds to the molecules of a substance, there is a relationship between moles and molecules, this relationship is Avogadro's number.
Avogadro's number tells us that a mole of any substance contains 6.022x10^23 molecules. Therefore in 16.4 moles of Kbr there will be:
[tex]\begin{gathered} \text{Formula units}=\text{Given moles}\times\frac{6.022\times10^{23}molecules}{1\text{ mol}} \\ \text{Formula units}=16.4\text{mol}\times\frac{6.022\times10^{23}molecules}{1\text{ mol}}=9.87\times10^{24}formulaunits \end{gathered}[/tex]The number of formula units of Kbr in 16.4 moles is 9.87x10^24
