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 empirical, or simplest formula for a compound is defined as the simplest whole number ratio of the atoms that make up the substance. Once the empirical formula has been determined, the molecular formula can be determined once the molar mass of the substance is known. This volume teaches when determining the empirical formula, it sometimes happens that the determined formula appears to contain fractions of atoms. When analyzing a substance to obtain it's percent composition, this information will only allow you to determine the simplest ratio of the atoms of the elements in the compound, not the actual molecular formula. The molar mass will be some integer multiple of the empirical mass.