How many atoms are in 1.50 moles of fluorine gas?

##1.81##x##10^24## atoms (3 s.f.)

Recall that moles can be converted to particles using Avogadro's constant (##6.022*10^23##) which is the number of molecules per mole of a substance.

In ##1.5## moles of fluorine gas, there are ##1.5*6.022*10^23## molecules of gas. However, since fluorine is diatomic (##F_2##), each molecule contains two atoms of fluorine. Thus, the number of atoms in ##1.5 mol## of ##F_2## is twice the number of molecules.

##:.## No. of atoms ##=2(1.5*6.022*10^23)=1.8066*10^24##

##=1.81*10^24## (3 s.f.), since there are 3 s.f. in ##1.50##.