Webb has calculated the percent composition of a compound. how can he check his result? by making sure they are in the lowest ratio by adding them to see if they total 100 by checking that they are whole-number multiples by dividing them by the molar mass

The percent composition of a compound will always be 100. Their may be many components present in the compound in different ratios then the percent composition gives the percent of components by mass of each element present in a compound.

For example there are three components in a compound a,b and c. Then the percent composition will be a+b+c = 100.

It can never exceed or be less than 100 in any condition.

i just learnt this recently but i need to look through my notes again