There are two iron atoms and three oxygen atoms in each molecule of Fe2O3. So that's five atoms per molecule.
One mole of any molecular substance contains <span>6.02×1023</span> molecules. Since there are two iron atoms in each of the molecules we're considering, there will be <span><span>(6.02×1023)</span>⋅2=1.204×1024</span> iron atoms in a whole mole of them.
But we're considering 0.550 mol, so multiply by 0.550:
<span>n=(0.550</span> mol<span>)⋅<span>(3.01×1024</span></span> atoms/mol<span>)=6.62×1023</span> iron atoms.
A good example is cigarretes they try to scare you into not smoking by telling you all of the downsides of smoking like lung cancer and i guess that would be fear appeal