How can the following questions be worked out: How many atoms of Iron are contained in 3 moles of Iron(III) oxide?

One mole in chemistry is defined as the number of unit
particles that are contained in 12 g of carbon-12. This is given as 6.02214179(30)*10^23
particles. The mass of one mole of any substance will have the same number of unit
particles.

In questions like the one you have given, where
you have to find the number of atoms contained in 3 moles of Iron(III) oxide, follow
these steps.

First look at the molecular composition of
Iron(III) oxide. It is Fe2O3, so one molecule of the iron oxide has 2 atoms of iron and
3 atoms of oxygen.

1 mole of Iron(III) oxide has 2 moles of
iron and 3 moles of oxygen.

The number of atoms of iron in
3 moles of Iron(III) oxide is 3*2*6.02214179(30)*10^23 or approximately
36.13285*10^23.