Answer:
Y = 92.5 %
Explanation:
Hello there!
In this case, since the reaction between lead (II) nitrate and potassium bromide is:

Exhibits a 1:2 mole ratio of the former to the later, we can calculate the moles of lead (II) bromide product to figure out the limiting reactant:

Thus, the limiting reactant is the KBr as it yields the fewest moles of PbBr2 product. Afterwards, we calculate the mass of product by using its molar mass:

And the resulting percent yield:

Regards!
There are three ways to measure the amount of something in chemistry.
1. There is a simple count which is tabulating the amount of something present.
2. You can measure the mass which is the amount of matter in something.
3. You can measure the volume which is the amount of three dimensional space occupied by a closed surface.
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.