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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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Ch. 9 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. Write a balanced equation 2.Identify known & unknown. 3. Convert known to mole (if necessary), line up conversion factors. 4. Use Mole Ratio. 5. Convert moles to unknown unit (if necessary). 6. Calculate and write units. known Mol of known Mol of unknown Mole ratio- get from equation Mol of unknown Units of unknown

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Mole - Mole Stoichiometry Formula: known mol mol unknown mol known 1.Write the known and unknown. 2.Use the balanced equation to find the mole ratio. 3.Calculate.

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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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Mass-Mass Stoichiometry Mass of reactants equals the mass of products, Law of Conservation of Mass ONLY mass and atoms are conserved in every chemical reaction 1. Write the known and unknown. 2. Find the molar mass of the known and unknown substances. 3. Use mole and molar mass conversion factors from Ch. 7 and mole ratios from the balanced equation to solve. 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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Volume-Volume Stoichiometry Formula to use: Known (L) 1 mol known mol unknown 22.4 L unknown L known mol known 1 mol unknown 1.Write the known and unknown. 2.Use mole and volume conversion factors from Ch. 7 and the mole ratios from the balanced equation to solve.

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C 3 H 8 + 5O 2 3CO 2 + 4H 2 O If 25 liters of oxygen are consumed in the above reaction, how many liters of carbon dioxide are produced? Volume-Volume Example #4

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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 Known: 9 moles O 2 Unknown: moles KClO 3

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Stoichiometry Problems 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 = g KClO 3 2 mol KClO 3 3 mol O g KClO 3 1 mol KClO 3 2KClO 3 2KCl + 3O 2 Known: 9.00 L O 2 Unknown: g KClO 3

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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 64 g Cu = 40.5 g Ag Cu + 2AgNO 3 2Ag + Cu(NO 3 ) 2 Known: 12.0 g Cu Unknown: g Ag 2 mol Ag 1 mol Cu 108 g Ag 1 mol Ag

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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 64 g Cu = 40.5 g Ag Cu + 2AgNO 3 2Ag + Cu(NO 3 ) 2 Known: 12.0 g CuUnknown: g Ag 2 mol Ag 1 mol Cu 108 g Ag 1 mol Ag

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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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To Determine Limiting Reagents 1. Write a balanced equation. 2. For each reactant, calculate the amount of product formed. 3. Smaller answer indicates: – limiting reactant – actual 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 = 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? L0.90 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? L0.90 L

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Limiting Reagents Zn: 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 (mathematical calculation used to make answer keys)

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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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B. Percent Yield 45.8 g K 2 CO 3 1 mol K 2 CO g K 2 CO 3 = g KCl 2 mol KCl 1 mol K 2 CO 3 74 g KCl 1 mol KCl K 2 CO 3 + 2HCl 2KCl + H 2 O + CO g? g actual: 46.3 g Theoretical Yield:

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B. Percent Yield Theoretical Yield = g KCl % Yield = 46.3 g g 100 = 94.3% K 2 CO 3 + 2HCl 2KCl + H 2 O + CO g49.12 g actual: 46.3 g

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