Chemistry - the Complete Course Series, teaches students quantitative reasoning to solve chemistry problems. The 30 volume series covers all aspects of Chemistry from density to the mole, to molarity, stoichiometry and equilibrium. It demonstrates how to ask meaningful questions and conduct careful investigations to build knowledge of chemical and physical concepts and develop the skills to solve mathematical and scientific problems. The term "percent composition" is always understood to mean percent composition by mass, even though it may not be specifically stated as such. Calculating the percent composition of a compound involves determining what percentage of the total mass of the compound is comprised of each of the elements present in the compound. This volume teaches sometimes the formula of the compound is given, and the percent composition can be determined from the formula. The term "empirical formula" is sometimes called the "simplest formula." the general concept of empirical formulas and how they are related to molecular formulas.