This document discusses chemical formulas and reactions. It explains that chemical formulas use symbols to represent elements and subscripts to show the number of each element. Empirical formulas show the simplest whole number ratio of elements, while molecular formulas show the actual number of atoms. Percent composition is used to determine the mass of each element in a compound as a percentage of the total mass. Examples are provided for calculating empirical and molecular formulas based on the percent composition or molar mass of elements in compounds.

1. Chemistry 30S Unit 3 – Chemical Reactions