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Ch 9 Stoichiometry Using Chemical Equations Ch 9 Stoichiometry Using Chemical Equations 1984, Union Carbide Plant – 10000+ killed in Bhopal, India by Methyl Isocyanate 1988 Pepcon, Henderson Rocket Fuel Explosion Ch 9 Stoichiometry Using Chemical Equations Objectives 1. To understand more of the information given in a balanced equation 2. To use a balanced equation to determine relationships between moles of reactant and products Ch 9 Stoichiometry Using Chemical Equations A. Information Given by Chemical Equations • A balanced chemical equation gives relative numbers of reactant and product molecules (or moles) that participate in a chemical reaction. • The coefficients of a balanced equation give the relative numbers of molecules (or moles). CO(g) + 2H2(g) CH3OH(l) How many moles of CH3OH will be produced from 1, 2, or 5 moles of CO? How many moles of hydrogen will react with 1, 2, or 5 moles of CO? Ch 9 Stoichiometry Using Chemical Equations B. Mole-Mole Relationships in a BALANCED Reaction • A balanced equation can predict the moles of product that a given number of moles of reactants will yield. What number of moles of O2 will be produced by the decomposition of 2, 1, or 5.8 moles of water? Ch 9 Stoichiometry Using Chemical Equations B. Mole-Mole Relationships using Factor Analysis • The mole ratio allows us to convert from moles of one substance in a balanced equation to moles of a second substance in the equation. Use dimensional/factor analysis and mole ratios to calculate the answers below: CH4(g) + 2O2(g) CO2 + 2H2O(l) 4.2 moles of CH4 reacts with how many moles of O2? 4.2 moles of CH4 will produce how many moles of H2O? Ch 9 Stoichiometry Using Chemical Equations Objectives 1. To learn to relate masses of reactants and products in a chemical reaction 2. To perform mass calculations that involve scientific notation Moles Grams Moles Grams Ch 9 Stoichiometry Using Chemical Equations A. Mass Calculations If 9.0 grams of water are decomposed to hydrogen and oxygen, what mass of oxygen gas is formed? Ch 9 Stoichiometry Using Chemical Equations C. Mass Calculations: Comparing Two Reactions • For equal masses of methane (CH4) and propane (C3H8), which will use more oxygen when fully burned? "Happy Mole Day to You" Chemistry Song Ch 9 Stoichiometry Using Chemical Equations Double Bacon Cheeseburgers and Stoichiometry • 1 Double Bacon Cheeseburger needs 1 bun, 2 patties, 2 slices of cheese, 4 strips of bacon • For 5 Double Bacon Cheeseburgers how many units of each ingredient do I need? • Fill in the final column below with how many complete burgers I can make: Buns Patties Cheese Slices Bacon Strips 2 4 4 8 4 4 8 16 16 30 32 48 How Many Burgers? Ch 9 Stoichiometry Using Chemical Equations Objectives 1. To understand the concept of limiting reactants 2. To learn to recognize the limiting reactant in a reaction 3. To learn to use the limiting reactant to do stoichiometric calculations 4. To learn to calculate percent yield Ch 9 Stoichiometry Using Chemical Equations A. The Concept of Limiting Reactants • Stoichiometric mixture – N2(g) + 3H2(g) 2NH3(g) Ch 9 Stoichiometry Using Chemical Equations A. The Concept of Limiting Reactants • Limiting reactant mixture – N2(g) + 3H2(g) 2NH3(g) Ch 9 Stoichiometry Using Chemical Equations A. The Concept of Limiting Reactants • For a Limiting reactant mixture the number of moles are not balanced to match the reaction equation – N2(g) + 3H2(g) 2NH3(g) – Limiting reactant is the reactant that runs out first – When the limiting reactant is exhausted, then the reaction stops Limiting Reactants Game Ch 9 Stoichiometry Using Chemical Equations B. Calculations Involving a Limiting Reactant Ch 9 Stoichiometry Using Chemical Equations B. Calculations Involving a Limiting Reactant Ch 9 Stoichiometry Using Chemical Equations C. Percent Yield • Theoretical Yield – The maximum amount of a given product that can be formed when the limiting reactant is completely consumed. • The actual yield (amount produced) of a reaction is usually less than the maximum expected (theoretical yield). • Percent Yield – The actual amount of a given product as the percentage of the theoretical yield. Ch 9 Stoichiometry Using Chemical Equations According to her pre-lab theoretical yield calculations a student’s experiment should have produced 1.44g of magnesium oxide. When she weighed her product after reaction, only 1.23g of magnesium oxide was present. What is the student’s percent yield?