Mole-Mole Ratios We’re about to embark on a wonderful journey through the land of chemical stoichiometry. Stoichiometry is just a fancy word to describe the math we use to determine relationships between reactants and/or products in a chemical reaction. Chemists use stoichiometry all the time, practically every day, but they don’t call it “stoichiometry.” They don’t call it anything, really. They just do the math. So, let’s not worry about fancy words, and let’s learn some chemistry math. Below, you see the equation that describes the reaction when propane combusts in oxygen to form water and carbon dioxide. What is wrong with this equation