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Mole Calculations

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? Visualizing a Chemical Reaction Na + Cl 2 NaCl ___ mole Cl 2 ___ mole NaCl___ mole Na

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___ mole NaCl 10 Visualizing a Chemical Reaction Na + Cl 2 NaCl ___ mole Cl 2 ___ mole Na

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Formation of Ammonia

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Proportional Relationships 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 Courtesy Christy Johannesson 150 cookies

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Proportional Relationships StoichiometryStoichiometry –mass relationships between substances in a chemical reaction –based on the mole ratio Mole RatioMole Ratio –indicated by coefficients in a balanced equation 2 Mg + O 2 2 MgO Courtesy Christy Johannesson

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Stoichiometry Steps 1. Write a balanced equation. 2. Identify known & unknown. 3. Line up conversion factors. –Mole ratio - moles moles –Molar mass -moles grams –Molarity - moles liters soln –Molar volume -moles liters gas Core step in all stoichiometry problems!! –Mole ratio - moles moles 4. Check answer. Courtesy Christy Johannesson

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1 mol of a gas=22.4 L at STP Molar Volume at STP S tandard T emperature & P ressure 0°C and 1 atm Courtesy Christy Johannesson

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Molar Volume at STP Molar Mass (g/mol) 6.02 particles/mol MASS IN GRAMS MOLES NUMBER OF PARTICLES LITERS OF SOLUTION Molar Volume (22.4 L/mol) LITERS OF GAS AT STP Molarity (mol/L) Courtesy Christy Johannesson

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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 Courtesy Christy Johannesson

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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 Courtesy Christy Johannesson O2O2 KClO 3 x mol KClO 3 = 9 mol O 2 = 6 mol KClO 3 2 mol KClO 3 3 mol O 2 6 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 Stoichiometry Problems 2KClO 3 2KCl + 3O 2 Courtesy Christy Johannesson

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How many grams of KClO 3 are required to produce 9.00 L of O 2 at STP? ? g9.00 L Stoichiometry Problems 2KClO 3 2KCl + 3O 2 Courtesy Christy Johannesson O2O2 KClO 3 x g KClO 3 = 9.00 L O L O 2 = 32.8 g KClO 3 1 mol O 2 2 mol KClO 3 3 mol O g KClO 3 1 mol KClO g

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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 2KClO 3 2KCl + 3O 2 Courtesy Christy Johannesson O2O2 KClO 3 x g KClO 3 = 9.00 L O L O 2 = 32.8 g KClO 3 1 mol O 2 2 mol KClO 3 3 mol O g KClO 3 1 mol KClO g

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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 + 2 AgNO 3 2 Ag + Cu(NO 3 ) 2 2 mol Ag 1 mol Cu g Ag 1 mol Ag 12.0 g? g Courtesy Christy Johannesson CuAg x g Ag = 12.0 g Cu g Cu = 40.7 g Ag 1 mol Cu 2 mol Ag 1 mol Cu g Ag 1 mol Ag 40.7 g

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use Avogadro’s number use molar mass Mole Calculations Volume, cm 3 Mass, gMolesAtoms use density g cm 3 x mol g x atoms mol x A graduated cylinder holds 25.4 cm 3 of mercury. If the density of mercury at 25 o C is g / cm 3, how many moles of mercury are in the cylinder? HINT: Volume of solids/liquids and moles are not directly connected. You must first use the density to convert the volume to a mass, and then derive the quantity of mercury, in moles, from the mass. Finally, the number of atoms is obtained from the number of moles. Kotz & Treichel, Chemistry & Chemical Reactivity, 3 rd Edition, 1996, page 93 How many atoms of mercury are there?

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Therefore, the mass of mercury is found to be equivalent to 344 g of mercury. Volume, cm 3 Mass, gMolesAtoms use densityuse molar mass use Avogadro’s number g cm 3 x mol g x g Hg 1 cm 3 Hg 25.4 cm 3 Hg =344 g Hg Knowing the mass, you can now find the quantity in moles.. 1 mol Hg g Hg 344 g Hg =1.71 mol Hg Finally, because you know the relation between atoms and moles (Avogodro’s number), you can now find the number of atoms in the sample x atoms Hg. 1 mol Hg 1.71 mol Hg =1.03 x atoms Hg A ABC B C Kotz & Treichel, Chemistry & Chemical Reactivity, 3 rd Edition, 1996, page 93 A graduated cylinder holds 25.4 cm 3 of mercury. If the density of mercury at 25 o C is g / cm 3, how many moles of mercury are in the cylinder? How many atoms of mercury are there? 344 g Hg 1.71 mol Hg atoms mol x

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2 Na + Cl 2 2 NaCl 2 grams 1 gram 2 grams W R O N G Violates Law of Conservation of Matter 2 atoms 1 molecule 2 molecules* *Better name would be “formula unit” 2 moles 1 mole 2 moles 100 g x Lx g NaCl 2 x L Cl 2 = 100 g Na 23 g Na = 49 L Cl 2 1 mol Na 1 mol Cl 2 2 mol Na 22.4 L Cl 2 1 mol Cl L Right side of room…calculate how many grams of NaCl will be produced from 100 g of Na. Left side of room…calculate how many grams of NaCl will be produced from L of Cl 2. NaNaCl x g NaCl = 100 g Na 23 g Na = 254 g NaCl 1 mol Na 2 mol NaCl 2 mol Na 58.5 g NaCl 1 mol NaCl Cl 2 NaCl x g NaCl = L Cl L Cl 2 = 254 g NaCl 1 mol Cl 2 2 mol NaCl 1 mol Cl g NaCl 1 mol NaCl

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Stoichiometry KClO 3 KCl + O gx gx L KClO 3 O2O2 x L O 2 = 500 g KClO g KClO 3 = 137 L O 2 1 mol KClO 3 3 mol O 2 2 mol KClO L O 2 1 mol O 2 KClO 3 KCl x g KCl = 500 g KClO g KClO 3 = 304 g KCl 1 mol KClO 3 2 mol KCl 2 mol KClO g KCl 1 mol KCl (304 g) (196 g) x g O 2 = 137 L O L O 2 = 196 g O 2 1 mol O 2 32 g O 2 1 mol O L

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Stoichiometry 2 TiO Cl CCO CO + 2 TiCl molx mol CCl 2 x mol C = 4.55 mol Cl 2 4 mol Cl 2 = 6.07 mol Cl 2 3 mol C CTiO 2 x molecules TiCl 4 = 115 g TiO 2 80 g TiO 2 = 8.66 x molecules TiCl 4 1 mol TiO 2 2 mol TiCl 4 2 mol TiO x molecules TiCl 4 1 mol TiCl 4 x g TiO 2 = 4.55 mol C 3 mol C = 243 g TiO 2 1 mol TiO 2 80 g TiO 2 2 mol TiO 2 How many moles of chlorine will react with 4.55 moles of carbon? How many grams of titanium (IV) oxide will react with 4.55 moles of carbon? x g How many molecules of TiCl 4 will react with 115 g TiO 2 ? TiO 2 TiCl 4 x molecules 115 g

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Stoichiometry Problems 1 Keys Stoichiometry Problems 1

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6.02 x atoms H 2 O 6.02x10 23 molecules H 2 O Which has more atoms: 30 g aluminum metal or 18 mL distilled water? x atoms Al = 30 g Al 27 g Al = 6.69 x atoms Al 1 mol Al 6.02 x atoms Al 1 mol Al How many atoms of aluminum are in 30 g of aluminum? Al x atoms Al = 30 g Al 27 g Al = 6.69 x atoms Al 6.02 x atoms Al Al x atoms = 18 mL H 2 O 1000 mL H 2 O = 1.45 x atoms 1 L H 2 O 1 mol H 2 O 22.4 L H 2 O How many atoms are in 18 mL of water? H2OH2O x atoms = 18 mL H 2 O 1 mL H 2 O = 1.81 x atoms 1 g H 2 O 1 mol H 2 O 18 g H 2 O How many atoms are in 18 mL of water? 1 mol H 2 O 3 atoms 1 molecule H 2 O 1 moL H 2 O 6.02x10 23 molecules H 2 O 3 atoms 1 molecule H 2 O W R O N G Recall, density of water LITERS is ONLY used for STP

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