Sometime it is important to know what percent of a compounds mass is due to a certain element. For example, a mining company may wish to know what percent of 400 tons of Fe2O3 is due to iron. They can then work out if it is worth trying to recover the iron from the sample of iron oxide.
Let us go straight into an example.
Calculate the percentage by mass of each element in carbon dioxide.
Continue with Cu(OH)2