Percentage composition is just a way to describe what proportions of the different elements there are in a compound.
If you have the formula of a compound, you should be able to work out thepercentage by mass of an element in it.
The formula for sodium hydroxide is NaOH. It contains three different elements:Na, O and H. But the percentage by mass of each element is not simply 33.3 per cent, because each element has a different relative atomic mass. You need…