Stoichiometry: Percent Composition Quiz

Percent composition is used to find the percentage of elements in a compound. One must know the molar mass of the elements and the compound in order to get percent composition. For instance, the percent composition of oxygen in water is 89%. The molar mass of water is 18g/mol, and oxygen has a molar mass of 16g/mol. 16 divided by 18 is .89. Multiply this by 100 and you get 89%. This leaves hydrogen making up 11% of the water compound. This quiz will cover basic percent composition problems. You will need a calculator and a periodic table. Select the best answer from the choices.