Stoichiometry Answer Key Vocabulary: Avogadro’s number, balanced equation, cancel, coefficient, dimensional analysis, molar mass, mole, molecular mass, stoichiometry Prior Knowledge Questions (Do these BEFORE using the Gizmo.) [Note: The purpose of these questions is to activate prior knowledge and get students thinking. Students are not expected to know the answers to the Prior Knowledge Questions.] 1. A 250 mL glass of orange juice contains 22 grams of sugar. How much sugar is in a two-liter (2,000 mL) bottle of orange juice? 176 grams of sugar 2. It requires two sticks of butter to make a batch of 20 cookies. How much butter will it take to make 150 cookies? 15 sticks of butter Gizmo Warm-up Just as a cook follows a recipe to decide how much of each ingredient to add, a chemist uses stoichiometry to determine the amounts of substances involved in chemical reactions. The Stoichiometry Gizmo™ allows you to try your hand at figuring out the amounts of reactants and products that take part in a chemical reaction. To begin, check that this equation is shown: Fe2O3 + 3CO 2Fe + 3CO2 1. Look at the coefficients (such as the “3” in 3CO) in front of each substance in the equation. The coefficients tell you how many molecules or atoms take part in a chemical reaction. In the spaces below, list the number of each molecule or atom in the equation: Fe2O3 1 CO 3 Fe 2 CO2 3 2. In a balanced equation, the same number of each kind of atom is shown on each side of the equation. Calculate the number of iron (Fe), oxygen (O), and carbon atoms (C). Reactants Iron: 2 Oxygen: 6 Carbon: 3 Products Iron: 2 Oxygen: 6 Carbon: 3