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Mole Review 1.) Calculate the number of moles in 60.4L of O 2. 2.) How many moles are there in 63.2g of Cl 2 ? 60.4L O L O 2 1 mol O 2 = 2.7 mol O g Cl 2 70g Cl 2 1mol Cl 2 = 0.903mol Cl 2

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Unit 08 Math In Chemistry Stoichiometry

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Tiny Tyke Tricycle Company F + S + 3W + H + 2P → FSW 3 HP 2 Scheduled to make 640 tricycles. How many wheels should they order? Proportional Relationships

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I have 5 eggs. How many cookies can I make? 3/4 c. brown sugar 1 tsp vanilla extract 2 eggs 2 c. chocolate chips Makes 5 dozen cookies. 2 1/4 c. flour 1 tsp. baking soda 1 tsp. salt 1 c. butter 3/4 c. sugar 5 eggs5 doz. 2 eggs = 12.5 dozen cookies Ratio of eggs to cookies

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Proportional Relationships Stoichiometry Stoichiometry – mass relationships between substances in a chemical reaction for example: you can determine the amount of a compound required to make another compound – based on the mole ratio Mole Ratio Mole Ratio – indicated by coefficients in a balanced equation 2 Mg + O 2 2 MgO 2 Moles of magnesium react with 1 mole of oxygen to form 2 moles of magnesium oxide.

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2 Mg + O 2 2 MgO What would be the mole ratio of magnesium to magnesium oxide? 2 : 2 Conversion factor = 2 mol Mg 2 mol MgO What would be the mole ratio of oxygen to magnesium? 1 : 2 Conversion factor = 1 mol O 2 (Mole Ratio) 2 mol Mg

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Practice 5 F 2 + 2NH 3 N 2 F 4 + 6HF 1. What is the mole ratio of NH 3 to F 2 ? Write the mole ratio as a conversion factor. 2. What is the mole ratio of HF to N 2 F 4 ? Write the mole ratio as a conversion factor. 2:5 2mol NH 3 5mol F 2 6:1 6mol HF 1mol N 2 F 4

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Stoichiometry Steps 1. Identify known & unknown. 2. Convert known to mole. (if necessary) 3. Use Mole Ratio. 4. Convert moles to unknown unit. (if necessary) known Mol of known Mol of unknown Mole ratio- get from equation Mol of unknown Units of unknown

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Mass-Mass Stoichiometry Mass of reactants equals the products Law of Conservation of Mass ONLY mass and atoms are conserved in every chemical reaction Known g 1 mol Known Molar mass Known mol unknown mol known Mol ratio- get from equation Molar mass unknown 1 mol unknown

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Mass-Mass Stoichiometry #1 The reaction of fluorine with ammonia produces dinitrogen tetrafluoride and hydrogen fluoride. 5F NH 3 → N 2 F 4 + 6HF How many grams of NH 3 are required to produce 7.38g HF?

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Mass-Mass Stoichiometry #2 5F NH 3 → N 2 F 4 + 6HF How many grams of N 2 F 4 can be produced from 265g F 2 ?

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Mass-Mass Stoichiometry #3 2C 2 H 2 + 5O 2 → 4CO 2 + 2H 2 O How many grams of oxygen are required to burn 52.0g C 2 H 2 ?

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C. Stoichiometry Problems How many grams of silver will be formed from 12.0 g copper? 12.0 g Cu 1 mol Cu g Cu = 40.7 g Ag Cu + 2AgNO 3 2Ag + Cu(NO 3 ) 2 2 mol Ag 1 mol Cu g Ag 1 mol Ag 12.0 g? g

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Calculate the number of grams of NH 3 produced by the reaction of 5.40 g of hydrogen with an excess of nitrogen. N 2 + 3H 2 → 2NH 3 C. Stoichiometry Problems

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Acetylen gas (C 2 H 2 ) is produced by adding water to calcium carbide (CaC 2 ). CaC 2 + 2H 2 O C 2 H 2 + Ca(OH) 2 How many grams of acetylene are produced by adding water to 5.00 g CaC 2 ? Using the same equation, determine how many moles of CaC 2 are needed to react completely with 49.0 g H 2 O.

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__S + __O 2 → __SO 3 Write the equation. Balance the equation. How many moles of SO 3 are produced when there are 4.5 moles of S ? Known = Unknown = Mole-Mole Examples #1

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2C 3 H 7 OH + 9O 2 → 6CO 2 + 8H 2 O Write the equation. Calculate the moles of oxygen needed to react with 3.40 moles of isopropyl alcohol. Mole-Mole Examples #2 Isopropyl alcohol (C 3 H 7 OH) burns in the air to this equation:

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2C 3 H 7 OH + 9O 2 → 6CO 2 + 8H 2 O Find the moles of water when 6.20 mol O 2 reacts with C 3 H 7 OH. Mole-Mole Examples #3

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C. Stoichiometry Problems How many moles of KClO 3 must decompose in order to produce 9 moles of oxygen gas? 9 mol O 2 2 mol KClO 3 3 mol O 2 = 6 mol KClO 3 2KClO 3 2KCl + 3O 2 ? mol9 mol

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Volume-Volume Stoichiometry Formula to use: Known (L) 1 mol known mol unknown L unknown L known mol known 1 mol unknown

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C 3 H 8 + 5O 2 → 3CO 2 + 4H 2 O If 20 liters of oxygen are consumed in the above reaction, how many liters of carbon dioxide are produced? Volume Example #4

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C. Mixed Stoichiometry Problems How many moles of KClO 3 must decompose in order to produce 9 moles of oxygen gas? 9 mol O 2 2 mol KClO 3 3 mol O 2 = 6 mol KClO 3 2KClO 3 2KCl + 3O 2 ? mol9 mol

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How many grams of KClO 3 are required to produce 9.00 L of O 2 at STP? 9.00 L O 2 1 mol O L O 2 = 32.8 g KClO 3 2 mol KClO 3 3 mol O g KClO 3 1 mol KClO 3 ? g9.00 L C. Mixed Stoichiometry Problems 2KClO 3 2KCl + 3O 2

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Limiting Reactants/Reagents Available Ingredients Available Ingredients – 4 slices of bread – 1 jar of peanut butter – 1/2 jar of jelly Limiting Reactant/Reagents Limiting Reactant/Reagents bread Excess Reactants/Reagents Excess Reactants/Reagents peanut butter and jelly

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Limiting Reactants/Reagents Limiting Reactant/Reagent Limiting Reactant/Reagent – used up in a reaction – determines the amount of product Excess Reactant/Reagent Excess Reactant/Reagent – added to ensure that the other reactant is completely used up – cheaper & easier to recycle

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Limiting Reagents 1. Write a balanced equation. 2. For each reactant, calculate the amount of product formed. 3. Smaller answer indicates: – limiting reactant – amount of product

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Limiting Reagents 79.1 g of zinc react with 0.90 L of HCl. Identify the limiting and excess reactants. How many liters of hydrogen are formed at STP? Zn + 2HCl ZnCl 2 + H g ? L 0.90 L

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Limiting Reagents 79.1 g Zn 1 mol Zn 65 g Zn = 27.3 L H 2 1 mol H 2 1 mol Zn 22.4 L H 2 1 mol H 2 Zn + 2HCl ZnCl 2 + H g ? L 0.90 L

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Limiting Reagents 0.90 L HCl 1 mol HCl 22.4 L HCl = 0.45 L H 2 1 mol H 2 2 mol HCL 22.4 L H 2 1 mol H 2 Zn + 2HCl ZnCl 2 + H g ? L 0.90 L

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Limiting Reagents Zn: 27.3 L H 2 HCl: 0.45 L H 2 Limiting reagent: HCl Excess reagent: Zn

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Percent Yield Percent yield- the ratio of the actual yield to the theoretical yield Actual yield- the amount of product formed when a reaction is carried out in the laboratory Theoretical yield- the calculated amount of product formed during a reaction

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Percent Yield calculated on paper measured in lab

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Percent Yield When 45.8 g of K 2 CO 3 react with excess HCl, 46.3 g of KCl are formed. Calculate the theoretical and % yields of KCl. K 2 CO 3 + 2HCl 2KCl + H 2 O + CO g? g actual: 46.3 g

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Mole - Mole Knownmol of unknown mol of known Mol Ratio – from equation Mass - Mass Known g molar mass known 1 mol known mol of unknown mol of known1 mol unknown molar mass unknown Known L 22.4 L known 1 mol known mol of unknown mol of known1 mol unknown 22.4 L unknown particles 6.02 × particles OR Other Formulas to Use

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Stoichiometry Problems How many moles of KClO 3 must decompose in order to produce 9 moles of oxygen gas? 9 mol O 2 2 mol KClO 3 3 mol O 2 = 6 mol KClO 3 2KClO 3 2KCl + 3O 2 ? mol9 mol

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Stoichiometry Problems How many grams of KClO 3 are req’d to produce 9.00 L of O 2 at STP? 9.00 L O 2 1 mol O L O 2 = 32.8 g KClO 3 2 mol KClO 3 3 mol O g KClO 3 1 mol KClO 3 ? g9.00 L 2KClO 3 2KCl + 3O 2

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Stoichiometry Problems How many grams of silver will be formed from 12.0 g copper? 12.0 g Cu 1 mol Cu g Cu = 40.7 g Ag Cu + 2AgNO 3 2Ag + Cu(NO 3 ) 2 2 mol Ag 1 mol Cu g Ag 1 mol Ag 12.0 g? g

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63.55 g Cu 1 mol Cu Stoichiometry Problems How many grams of Cu are required to react with 1.5 L of 0.10M AgNO 3 ? 1.5 L.10 mol AgNO 3 1 L = 4.8 g Cu Cu + 2AgNO 3 2Ag + Cu(NO 3 ) 2 1 mol Cu 2 mol AgNO 3 ? g 1.5L 0.10M

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