VIEWS: 75 PAGES: 18 POSTED ON: 1/6/2011
Reaction Stochiometry Chapter 3 Balancing Reactions • Law of Conservation of Mass – There is no detectable change in quantity of matter in an ordinary chemical reaction. 1. C7H16 burns in oxygen to form carbon dioxide and water C7H16 + 11 O2 7 CO2 + 8 H2O 2. Propane, C3H8 burns in oxygen to form carbon dioxide and water Balancing Reactions 3. NH3 burns in oxygen to form NO & water Balance the following reactions: 1) Na + Cl2 NaCl 2) N2 + H2 NH3 3) Fe + O2 Fe2O3 4) Cu + AgNO3 Ag + Cu(NO3)2 5) H2SO4 + NaCN HCN + Na2SO4 6) Fe2O3 + CO Fe + CO2 Calculations using Chemical Equations Fe2 O3 + 3 CO 2 Fe + 3 CO2 1. How many iron atoms can be produced by the reaction of 2.50 x 105 formula units of iron (III) oxide with excess carbon monoxide 2 Fe atoms ? Fe atoms = 2.50 10 formula units Fe 2O 3 5 1 formula units Fe 2O 3 5.00 10 5 Fe atoms Calculations using Chemical Equations Fe2 O3 + 3 CO 2 Fe + 3 CO2 2. What mass of CO is required to react with 146 g of iron (III) oxide? 76.8 g CO 3. What mass of carbon dioxide can be produced by the reaction of 0.540 mole of iron (III) oxide with excess carbon monoxide? 71.3 g CO2 Calculations using Chemical Equations Fe2 O3 + 3 CO 2 Fe + 3 CO2 4. What mass of iron (III) oxide reacted with excess carbon monoxide if the carbon dioxide produced by the reaction had a mass of 8.65 grams? 10.5 g Fe2O3 5. How many pounds of carbon monoxide would react with 125 pounds of iron (III) oxide? 65.7 lb CO Calculations using Chemical Equations Using the following equation: NaOH + H2SO4 H2O + Na2SO4 How many grams of sodium sulfate will be formed if you start with 200 grams of sodium hydroxide and you have an excess of sulfuric acid? 355 grams of Na2SO4 • Calculations Using Chemical Equations Using the following equation: Pb(SO4)2 + LiNO3 Pb(NO3)4 + Li2SO4 How many grams of lithium nitrate will be needed to make 250 grams of lithium sulfate, assuming that you have an adequate amount of lead (IV) sulfate to do the reaction? 313 grams of LiNO3 Limiting Reagent Concept Calculations: Limiting Reagent 1. What is the maximum mass of sulfur dioxide that can be produced by the reaction of 95.6 g of carbon disulfide with 110. g of oxygen? CS2 3 O2 CO2 2 SO2 CS2 3 O 2 CO2 2 SO 2 1 mol CS2 2 mol SO 2 64.1 g SO 2 ? g SO 2 95.6 g CS2 161 g SO 2 76.2 g 1 mol CS2 1 mol SO 2 1 mol O 2 2 mol SO 2 64.1 g SO 2 ? g SO 2 110 g O 2 147 g SO 2 32.0 g O 2 3 mol O 2 1 mol SO 2 • Which is limiting reactant? • Limiting reactant is O2. • What is maximum mass of sulfur dioxide? • Maximum mass is 147 g. Calculations: Limiting Reagent The reaction between aluminum and iron (III) oxide can generate temperatures approaching 3000oC and is used in welding metals: 2Al + Fe2O3 Al2O3 + 2Fe In one process, 124g of Al are reacted with 601g of Fe2O3. (a) Calculate the mass (g) of Al2O3 formed. (b) How much of the excess reagent is left at the end of the reaction? 234 grams of Al2O3 234 grams 3. The depletion of ozone (O3) in the stratosphere has been a matter of great concern among scientists in recent years. It is believed that ozone can react with nitric oxide (NO) that is discharged from the high-altitude jet plane, the SST. The reaction is O3 + NO O2 + NO2 If 0.740g of O3 reacts with 0.670g of NO, how many grams of NO2 will be produced? Which compound is the limiting reagent? Calculate the number of moles of the excess reagent in this reaction. 0.709 g of NO2 O3 6.9x10-3 mol NO Reaction Yield • Theoretical Yield – Amount of product based on the limiting reagent – Assumes all the limiting reagent reacted • Actual Yield – Amount of product obtained from the reaction – Experiment • Percent Yield actual yield %yield x 100% theoretical yield Initially, vanadium metal, which is used in steel alloys, can be obtained by reacting vanadium(V) oxide with calcium at high temperatures: 5Ca + V2O5 5CaO + 2V In one process, 1.54x103 g of V2O5 react with 1.96x103 g of Ca. (a) Calculate the theoretical yield of V. (b) Calculate the percent yield if 803 g of V are obtained. 863 g V 93.0% Assignment Chapter 3 # 83, 85, 89, 91
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