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Stoichiometry Chemistry Matter and Change Chapter 11 CHAPTER 11 BIG IDEA Mass relationships in chemical reactions confirm the law of conservation of mass Chemistry Matter and Change 11.1 Defining Stoichiometry 11.1 MAIN IDEA The amount of each reactant present at the start of a chemical reaction determines how much product can form. 11.1 OBJECTIVES Describe the types of relationships indicated by a balanced chemical reaction. State the mole ratios from a balanced chemical reaction. 11.1 REVIEW VOCABULARY Chemical reaction Reactant Product Q: Why was the mole of oxygen molecules excited when he walked out of the singles bar? A: He got Avogadro's number! 11.1 NEW VOCABULARY Stoichiometry Mole ratio Composition stoichiometry Reaction stoichiometry Cookies Ingredients 2 1/4 cups all-purpose flour 1 teaspoon baking soda 1 teaspoon salt 1 cup butter, softened 3/4 cup granulated sugar 3/4 cup packed brown sugar 1 teaspoon vanilla extract 2 large eggs 2 cups (12-oz. pkg.) NESTLÉ® TOLL HOUSE® Semi-Sweet Chocolate Morsels 1 cup chopped nuts Yield: 5 dozen cookies If you have only one egg, how many cookies can you make? What information do you need? Cookies Ingredients 2 1/4 cups all-purpose flour 1 teaspoon baking soda 1 teaspoon salt 1 cup butter, softened 3/4 cup granulated sugar 3/4 cup packed brown sugar 1 teaspoon vanilla extract 2 large eggs 2 cups (12-oz. pkg.) NESTLÉ® TOLL HOUSE® Semi-Sweet Chocolate Morsels 1 cup chopped nuts Yield: 5 dozen cookies If you have only one egg, how many cookies can you make? 1 egg 60 cookies 2 egg = 30 cookies Cookies Ingredients 2 1/4 cups all-purpose flour 1 teaspoon baking soda 1 teaspoon salt 1 cup butter, softened 3/4 cup granulated sugar 3/4 cup packed brown sugar 1 teaspoon vanilla extract 2 large eggs 2 cups (12-oz. pkg.) NESTLÉ® TOLL HOUSE® Semi-Sweet Chocolate Morsels 1 cup chopped nuts Yield: 5 dozen cookies If you need to make 100 cookies, how much flour do you need? What information do you need? Cookies Ingredients 2 1/4 cups all-purpose flour 1 teaspoon baking soda 1 teaspoon salt 1 cup butter, softened 3/4 cup granulated sugar 3/4 cup packed brown sugar 1 teaspoon vanilla extract 2 large eggs 2 cups (12-oz. pkg.) NESTLÉ® TOLL HOUSE® Semi-Sweet Chocolate Morsels 1 cup chopped nuts Yield: 5 dozen cookies If you need to make 100 cookies, how much flour do you need? What information do you need? 100 cookies 2.25 Cups flour 60 cookies = 3.75 C flour Cookies Ingredients 2 1/4 cups all-purpose flour 1 teaspoon baking soda 1 teaspoon salt 1 cup butter, softened 3/4 cup granulated sugar 3/4 cup packed brown sugar 1 teaspoon vanilla extract 2 large eggs 2 cups (12-oz. pkg.) NESTLÉ® TOLL HOUSE® Semi-Sweet Chocolate Morsels 1 cup chopped nuts Yield: 5 dozen cookies If you have 3 teaspoons of salt and 5 eggs, how many cookies can you make? Cookies Ingredients 2 1/4 cups all-purpose flour 1 teaspoon baking soda 1 teaspoon salt 1 cup butter, softened 3/4 cup granulated sugar 3/4 cup packed brown sugar 1 teaspoon vanilla extract 2 large eggs 2 cups (12-oz. pkg.) NESTLÉ® TOLL HOUSE® Semi-Sweet Chocolate Morsels 1 cup chopped nuts Yield: 5 dozen cookies 3 t salt 60 cookies = 180 cookies 1 t salt 5 eggs 60 cookies 2 eggs = 150 cookies Reactions are Recipes Stoichiometry • Two types – Composition stoichiometry: deals with mass relationships of elements in a compound – Reaction stoichiometry: deals with the mass relationships between products and reactants in a chemical reaction The Key is MOLE RATIOS • All chemical reactions are described in moles • You can convert moles of one substance to moles of another substance given a BALANCED EQUATION Recall Moles Practice • For the equation – N2+3H22NH3 – What is the mole ratio for nitrogen to hydrogen? 1 mole N2 3 mole H2 =1 – What is the mole ratio for hydrogen to ammonia? 3 mole H2 2 mole NH3 =1 1 mole N2 2 mole NH3 =1 – What is the mole ratio for nitrogen to ammonia? C6H12O6 + 6 O2 6 H2O + 6 CO2 • reaction reactiontype:______________________ type:______________________ • If 12 was consumed, howhow 12 moles molesofofoxygen oxygen was consumed, many were manymoles molesofofCO C26H were consumed? 12O6produced? 2H2O2 2H2O + O2 • reaction reaction type:______________________ type:______________________ • If 3 moles produced,what what is is the molesofHoxygen consumed, 2O2 areare mass thatthat wasisproduced? massofofwater oxygen produced? CAN YOU… Describe the types of relationships indicated by a balanced chemical reaction. State the mole ratios from a balanced chemical reaction. Chemistry Matter and Change 11.2 Stoichiometric Calculations 11.2 MAIN IDEA The solution to every stoichiometry problem requires a balanced chemical reaction. 11.2 OBJECTIVES List the sequence of steps used in solving stoichiometric problems. Solve stoichiometric problems. 11.2 REVIEW VOCABULARY Chemical reaction Diatomic element Are you part of the solution or part of the precipitate? The formula that always works: • You may not always need the whole thing g “A” Given mol “A” mol “B” g “B” g “A” mol “A” mol “B” Balanced equation Periodic table Periodic table 2 NaOH + 1 CaBr2 2 NaBr + 1 Ca(OH)2 • reaction type:______________________ • If 27.3 g NaOH is consumed, how many moles of calcium hydroxide are produced? • If 84.2 g of calcium bromide are consumed, how many moles of sodium hydroxide are consumed? 3 Pb + 2 H3PO4 3 H2 + 1 Pb3(PO4)2 • reaction type:______________________ • If 14.7 g of lead is consumed, what mass of hydrogen was produced? • If 87.24 g of Lead phosphate needs to be produced, what mass of phosphoric acid is needed? CAN YOU… List the sequence of steps used in solving stoichiometric problems. Solve stoichiometric problems. Chemistry Matter and Change 11.3 Limiting Reactants 11.3 MAIN IDEA A chemical reaction stops when one of the reactants is used up. 11.3 OBJECTIVES Identify the limiting reactant in a chemical equation. Identify the excess reactant and calculate the amount remaining after the reaction is complete. Calculate the mass of a product when the amounts of more than one reactant are given. Calculate the maximum yield and amount of excess reactant remaining. 11.3 MAIN IDEA Percent yield is a measure of the efficiency of a reaction. 11.3 NEW VOCABULARY Limiting reactant Excess reactant 11.3 REVIEW VOCABULARY Molar mass Q: What do you call a tooth in a glass of water? A: One molar solution. Limiting Reagent • You have 16 T PB, 8 TB jelly and 4 slices of bread. • Which one is the limiting reagent? • Which are the excess reagents? Limiting reagent problems 1. Calculate the yield of any of the products (If you have to solve for one, use that one and save yourself some steps!) 2. The one that gave you the least amount of product is the limiting reactant 3. All others are excess reactants If you have 8 car bodies and 36 tires, what will you have left over and how many complete cars will you have? 4 tires + 1 body 1 car • Given 8 bodies and 36 tires 8 bodies 1 car = 8 cars 1 body 36 tires 1 car 4 tires = 9 cars limiting What is left over? • Calculate what you used then subtract 8 cars 4 tires 1 car 36 tires - 32 tires 4 tires = 32 tires 2.00 g sample of ammonia is mixed with 4.00 g of oxygen. Which is the limiting reactant and how much excess reactant remains after the reaction has stopped? • 4 NH3(g) + 5 O2(g) 4 NO(g) + 6 H2O(g) A How much is left? • Figure out how much was used and subtract from the initial amount CAN YOU… Identify the limiting reactant in a chemical equation. Identify the excess reactant and calculate the amount remaining after the reaction is complete. Calculate the mass of a product when the amounts of more than one reactant are given. Calculate the maximum yield and amount of excess reactant remaining. Chemistry Matter and Change 11.4 Percent Yield 11.4 OBJECTIVES Calculate the theoretical yield of a chemical reaction from data. Determine the percent yield for a chemical reaction. 11.4 REVIEW VOCABULARY Process Yield Q: What is the name of 007's Eskimo cousin? A: Polar Bond. 11.4 NEW VOCABULARY Theoretical yield Actual yield Percent yield Theoretical yield • Calculated value • If 120. g of propane, C3H8, is burned in excess oxygen, how many grams of water are formed? Actual yield • The amount measured (actual) • If 120. g of propane, C3H8, is burned in excess oxygen and 140. g of water are formed, what is the percent yield? actual % yield 100 theoretica l Percent Yield • Theoretical: 196 g water • Actual: 140. g water 140 g water % yield 100 196 g water 71.4% yield CAN YOU… Calculate the theoretical yield of a chemical reaction from data. Determine the percent yield for a chemical reaction.