* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download CHAPTER 9 Notes
Electrochemistry wikipedia , lookup
Photoredox catalysis wikipedia , lookup
Liquid–liquid extraction wikipedia , lookup
History of molecular theory wikipedia , lookup
Lewis acid catalysis wikipedia , lookup
Chemical thermodynamics wikipedia , lookup
Electrolysis of water wikipedia , lookup
Asymmetric induction wikipedia , lookup
Self-assembled monolayer wikipedia , lookup
Kinetic resolution wikipedia , lookup
Atomic theory wikipedia , lookup
Computational chemistry wikipedia , lookup
Chemical reaction wikipedia , lookup
Isotopic labeling wikipedia , lookup
Resonance (chemistry) wikipedia , lookup
Chemical equilibrium wikipedia , lookup
Supramolecular catalysis wikipedia , lookup
Click chemistry wikipedia , lookup
Biochemistry wikipedia , lookup
Process chemistry wikipedia , lookup
Physical organic chemistry wikipedia , lookup
Photosynthetic reaction centre wikipedia , lookup
Implicit solvation wikipedia , lookup
Gas chromatography–mass spectrometry wikipedia , lookup
Transition state theory wikipedia , lookup
Rate equation wikipedia , lookup
George S. Hammond wikipedia , lookup
Determination of equilibrium constants wikipedia , lookup
Geometrical frustration wikipedia , lookup
CHAPTER 9: STOICHIOMETRY 9.1 Interpreting a chemical Equation H2 (g) + 1 molecule N2 ____molecule(s) Cl2 (g) 1 molecule + 2 HCl (g) 2 molecules 3 H2 (g) ____molecule(s) 2 NH3 (g) ____molecule(s) It follows that any multiples of these coefficients will be in same ratio! 2 H2 (g) O2 (g) + X 1000 ____molecule(s) XN ____molecule(s) 2 H2O (g) ____molecule(s) ____ molecule(s) ____molecule(s) ____ molecule(s) Since N=Avogadro’s # = 6.02x1023 molecules = 1 mol 2 H2 (g) + ____mol (s) O2 (g) 2 H2O (g) ____mol (s) ____ mol (s) Thus, the coefficients in a chemical equation give the mole ratios of reactants and products in a reaction. Give the mole ratios for each of the following: 1. H2 (g) + ____mol(s) 2. C3H8 (g) ____mol(s) Cl2 (g) 2 HCl (g) ____mol(s) + 5 O2 (g) ____mol(s) ____mol(s) 3 CO2 (g) ____mol(s) + 4 H2O (g) ____mol(s) 1 9.2 MOLE-MOLE RELATIONSHIPS Consider the following reaction: C3H8 (g) + 5 O2 (g) 3 CO2 (g) + 4 H2O (g) 1. Use unit factors to determine how many moles of O2 are needed to completely react with 2.25 moles of C3H8. 2. How many moles of CO2 form when 3.50 moles of O2 react? 3. How many moles of H2O form when 4.75 moles of CO2 form? 4. How many moles of C3H8 are required to produce 1.50 moles of H2O? 2 9.3 Stoichiometry Problems stoichiometry (STOY-key-OM-etry): -refers to the amounts of reactants and products in a chemical reaction -a stoichiometry problem generally involves relating amounts of reactants and/or products to each other in terms of moles 9.4 Mass-Mass (Stoichiometry) Problems Molar MASS OF KNOWN Mole-Mole MOLES OF KNOWN Mass Molar MOLES OF UNKNOWN Ratio MASS OF UNKNOWN Mass Example: Consider the mass of CO needed to react completely with 50.0 g of Fe2O3. Fe2O3 (s) + 3 CO 2 Fe (s) + 3 CO2 (g) 1. Calculate the mass of CO needed to react completely with 50.0 g of Fe2O3. 2. Calculate the mass of iron produced when 123 g of CO reacts completely. 3. Calculate the mass of CO2 produced when 75.0 g of iron is produced. 3 9.5 The Limiting Reactant Concept (LIMITING REAGENT) In practice, reactants will not always be present in the exact amounts necessary for all reactants to be converted completely into products. Some reactants (usually the least expensive) are present in larger amounts and are never completely used up “reactant(s) in excess” Only in a limited supply of the other reactants (usually the more expensive) are present, so these are completely used up “limiting reactant” since it limits the amount of product that can be made MAKING BICYCLES -Parts needed: - 1 bicycle frame - 1 seat - 2 pedals - 2 wheels (rims + tires) Example: How many bicycles can be made with 5 frames, 6 seats, 15 pedals and 8 wheels? (Indicate the limiting reactant and reactants in excess.) 4 MAKING BISQUICK TM PANCAKES 2 cups Bisquick 1 cup milk 2 eggs 14 pancakes 2 cups of BisquickTM + 1 Cup milk + 2 eggs 14 pancakes Example: If you have 10 cups of BisquickTM, 10 cups of milk, and 12 eggs, how many pancakes can you make? (Indicate the limiting reagent(s) and reagent(s) in excess.) 9.6 Limiting Reactant Problems GUIDELINES FOR SOLVING LIMITING REAGENT PROBLEMS: 1. Calculate the amount (moles or mass) of product formed using the amount of each reactant given -Use mass-mass conversions Smallest amount = amount of product formed! 2. Whichever reactant produces the smaller amount of product limiting reagent 3. All other reactant(s) in excess 5 Ex. 1: Consider the reaction between aluminum metal and hydrochloric acid to produce hydrogen gas: 2 Al(s) + 6 HCl (aq) 2 AlCl3 (aq) + 3 H2 (g) Calculate the number of moles of hydrogen gas produced when 5.00 moles of aluminum metal react with 5.00 moles of HCl. Limiting reactant = ____________________ Reactant in excess =___________________ Ex. 2: Consider the reaction fro propane (C3H8) burning: C3H8 (g) + 5 O2 (g) 3 CO2 (g) + 4 H2O (g) Calculate the number of moles of Carbon dioxide gas produced. When 1.50 moles of propane react with 5.00 moles of oxygen. Limiting reactant = ____________________ Reactant in excess =___________________ 6 actual yield 9.7 Percent yield = x 100% theoretical yield theoretical yield: Amount of product one should get based on the chemical equation and the amount of reactants present -One generally calculates this in grams from info given Actual yield: Amount of produce one actually obtains -Generally smaller than the theoretical yield because of impurities and other adverse conditions in the lab -This value has to be provided in a problem Ex.: Calculate the percent yield for a reaction with a theoretical yield of 75.0 g of carbon dioxide if the actual amount of carbon dioxide produced was 59.2 g. 7 Example: Consider the following equation: 2 K + Cl2 2 KCl a. How many grams of KCl is produced from 2.50 g of K and excess Cl2. b. From 1.00 g of Cl2 and excess K? c. When 2.50 g of K and 1.00 g Cl2 react together, the mass of KCl produced is _________________________, the limiting reactant is_________________, and the reactant in excess is _________________________. d. Calculate the percent yield if 86.7 g of KCl is actually produced when 2.50 g of K and 1.00g Cl2 react. 8 CHAPTER 9: STOICHIOMETRY 9.6 Interpreting a chemical Equation H2 (g) + 1 molecule N2 _1___molecule(s) Cl2 (g) 1 molecule + 2 HCl (g) 2 molecules 3 H2 (g) 2 NH3 (g) __3__molecule(s) __2__molecule(s) It follows that any multiples of these coefficients will be in same ratio! 2 H2 (g) + O2 (g) _1000___molecule(s) _2000___ molecule(s) X 1000 _2000___molecule(s) XN 2 H2O (g) 1.204 x 1023 molecule(s) 6.02 x 1023 molecule(s) 1.204 x 1023 molecule(s) Since N=Avogadro’s # = 6.02x1023 molecules = 1 mol 2 H2 (g) + _2___mol (s) O2 (g) 2 H2O (g) __1__mol (s) __2__ mol (s) Thus, the coefficients in a chemical equation give the mole ratios of reactants and products in a reaction. Give the mole ratios for each of the following: 1. H2 (g) + __1_mol(s) 2. C3H8 (g) _1__mol(s) Cl2 (g) __1_mol + 2 HCl (g) __2_mol(s) 5 O2 (g) __5_mol(s) 3 CO2 (g) _3__mol(s) + 4 H2O (g) __4_mol(s) 9 9.7 MOLE-MOLE RELATIONSHIPS Consider the following reaction: C3H8 (g) + 5 O2 (g) 3 CO2 (g) + 4 H2O (g) 4. Use unit factors to determine how many moles of O2 are needed to completely react with 2.25 moles of C3H8. 2.25 mol C3H8 x 5 mol O2 1 mol C3H8 = 11.3 mol O2 5. How many moles of CO2 form when 3.50 moles of O2 react? 3.50 mol O2 x 3 mol CO2 5 mol O2 = 2.10 mol CO2 6. How many moles of H2O form when 4.75 moles of CO2 form? 4.74 mol CO2 x 4 mol H2O 3 mol CO2 = 6.33 mol H2O 4. How many moles of C3H8 are required to produce 1.50 moles of H2O? 1.50 mol H2O x 1 mol C3H8 4 mol H2O = 0.375 mol C3H8 10 9.8 Stoichiometry Problems stoichiometry (STOY-key-OM-etry): -refers to the amounts of reactants and products in a chemical reaction -a stoichiometry problem generally involves relating amounts of reactants and/or products to each other in terms of moles 9.9 Mass-Mass (Stoichiometry) Problems Molar MASS OF KNOWN Mole-Mole MOLES OF KNOWN Mass Molar MOLES OF UNKNOWN Ratio MASS OF UNKNOWN Mass Example: Consider the mass of CO needed to react completely with 50.0 g of Fe2O3. Fe2O3 (s) + 3 CO 2 Fe (s) + 3 CO2 (g) 4. Calculate the mass of CO needed to react completely with 50.0 g of Fe2O3. Given: 50.0 g Fe2O3 Find: g CO Format: g Fe2O3 mol Fe2O3 mol CO g CO 50.0 g Fe2O3 x 1 mol Fe2O3 x 3 mol CO x 160. g Fe2 O3 1 mol Fe2O3 28.0 g CO 1 mol CO = 26.3 g CO 5. Calculate the mass of iron produced when 123 g of CO reacts completely. Given: 123 g CO Find: g Fe Format: g CO mol CO mol Fe g Fe 123 g CO x 1 mol CO 28.0 g CO x 2 mol Fe x 3 mol CO 55.8 g Fe 1 mol Fe = 163 g Fe 6. Calculate the mass of CO2 produced when 75.0 g of iron is produced. Given: 75.0 g Fe Find: g CO2 Format: g Fe mol Fe mol CO2 g CO2 75.0 g Fe x 1 mol Fe 55.8 g Fe x 3 mol CO2 x 2 mol Fe 44.0 g CO2 1 mol CO2 = 88.7 g CO2 11 9.10 The Limiting Reactant Concept (LIMITING REAGENT) In practice, reactants will not always be present in the exact amounts necessary for all reactants to be converted completely into products. Some reactants (usually the least expensive) are present in larger amounts and are never completely used up “reactant(s) in excess” Only in a limited supply of the other reactants (usually the more expensive) are present, so these are completely used up “limiting reactant” since it limits the amount of product that can be made MAKING BICYCLES -Parts needed: - 1 bicycle frame - 1 seat - 2 pedals - 2 wheels (rims + tires) Example: How many bicycles can be made with 5 frames, 6 seats, 15 pedals and 8 wheels? (Indicate the limiting reactant and reactants in excess.) 1 bicycle frame + 1 seat + 2 pedals + 2 wheels = 1 bicycle 5 frames x 1 bike = 5 bikes 1 frame 6 seats x 1 bike = 6 bikes 1 seat 15 pedals x 1 bike = 7.5 bikes 2 pedals 12 8 wheels x 1 bike = 4 bikes 2 wheels Limiting reactant – wheels Excess reactants – Bicycle frames, seats, pedals MAKING BISQUICK TM PANCAKES 2 cups Bisquick 1 cup milk 2 eggs 14 pancakes 2 cups of BisquickTM + 1 Cup milk + 2 eggs 14 pancakes Example: If you have 10 cups of BisquickTM, 10 cups of milk, and 12 eggs, how many pancakes can you make? (Indicate the limiting reagent(s) and reagent(s) in excess.) 2 c Bisquick + 1 C milk + 2 eggs = 14 pancakes 10 c. Bisquick x 14 pancakes = 70 pancakes 2 c. Bisquick 10 c milk x 14 pancakes = 140 pancakes 1 c milk 12 eggs x 14 pancakes = 84 pancakes 2 eggs Limiting reagent = Bisquick Excess reagent = milk, eggs 13 9.6 Limiting Reactant Problems GUIDELINES FOR SOLVING LIMITING REAGENT PROBLEMS: 4. Calculate the amount (moles or mass) of product formed using the amount of each reactant given -Use mass-mass conversions Smallest amount = amount of product formed! 5. Whichever reactant produces the smaller amount of product limiting reagent 6. All other reactant(s) in excess Ex. 1: Consider the reaction between aluminum metal and hydrochloric acid to produce hydrogen gas: 2 Al(s) + 6 HCl (aq) 2 AlCl3 (aq) + 3 H2 (g) Calculate the number of moles of hydrogen gas produced when 5.00 moles of aluminum metal react with 5.00 moles of HCl. + 6 HCl 2 AlCl3 + 3 H2 2 Al 5.00 mol Al x 3 mol H2 = 7.5 mol H2 2 mol Al 5.00 mol HCl x 3 mol H2 = 2.5 mol H2 6 mol HCl Limiting reactant = ___HCl____________ Reactant in excess =_______Al____________ Ex. 2: Consider the reaction fro propane (C3H8) burning: C3H8 (g) + 5 O2 (g) 3 CO2 (g) + 4 H2O (g) Calculate the number of moles of Carbon dioxide gas produced. When 1.50 moles of propane react with 5.00 moles of oxygen. C3H8 + 5 O2 3 CO2 + 4 H2O 1.50 mol C3H8 x 3 mol CO2 = 4.5 mol CO2 1 mol C3H8 14 5.00 mol O2 x 3 mol CO2 = 3 mol CO2 5 mol O2 Limiting reactant = _____O2_________ Reactant in excess =_________C3H8__________ actual yield 9.7 Percent yield = x 100% theoretical yield theoretical yield: Amount of product one should get based on the chemical equation and the amount of reactants present -One generally calculates this in grams from info given Actual yield: Amount of produce one actually obtains -Generally smaller than the theoretical yield because of impurities and other adverse conditions in the lab -This value has to be provided in a problem Ex.: Calculate the percent yield for a reaction with a theoretical yield of 75.0 g of carbon dioxide if the actual amount of carbon dioxide produced was 59.2 g. 59.2 g CO2 x 100 = 78.9% 75.0 g CO2 15 Example: Consider the following equation: 2 K + Cl2 2 KCl a. How many grams of KCl is produced from 2.50 g of K and excess Cl2. Given: 2.50 g K Find: g KCl Format: g K mol K mol KCl g KCl 2.50 g K x 1 mol K x 2 mol KCl x 74.6 g KCl = 4.77 g KCl 39.1 g K 2 mol K 1 mol KCl b. From 1.00 g of Cl2 and excess K? Given: 1.00 g Cl2 Find: g KCl Format: g Cl2 mol Cl2 mol KCl g KCl 1.00 g Cl2 x 1 mol K x 2 mol KCl x 74.6 g KCl = 2.10 g KCl 1 mol KCl 70.9 g Cl2 1 mol Cl2 c. When 2.50 g of K and 1.00 g Cl2 react together, the mass of KCl produced is _____2.10 g_______________, the limiting reactant is____Cl2____________, and the reactant in excess is _______K__________________. d. Calculate the percent yield if 86.7 g of KCl is actually produced when 2.50 g of K and 1.00g Cl2 react. 16 86.7 x 100 = 4130% 2.10 17