Chapter 3: Stoichiometry of Formulas and Equations

Avogadro’s number (6.022 × 10²³ entities/mol) is introduced as the key conversion factor linking particles to moles, while molar mass connects mass in grams to the amount in moles. Students learn to perform conversions among mass, amount, and number of chemical entities using dimensional analysis. The importance of mass percent composition is also highlighted, allowing for the identification of unknown compounds and comparisons between empirical and molecular formulas. The chapter then transitions to chemical equations as a tool for representing chemical reactions, emphasizing the need for balanced equations that conform to the law of conservation of mass. Students learn to identify reactants and products, balance chemical equations by inspection, and interpret mole-to-mole relationships derived from coefficients. These balanced equations serve as the foundation for stoichiometric calculations, enabling students to predict the amount of product formed or reactant required in a chemical reaction. Special cases such as sequential reactions, limiting reactants, excess reagents, and percent yield are explored in detail, with examples that demonstrate how to approach multi-step problems and understand reaction efficiency. By mastering these stoichiometric tools, students can analyze chemical formulas, quantify reactions, and apply these skills to topics like solution concentration, gas laws, and thermochemistry in later chapters.