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Copyright©2004 by Houghton Mifflin Company. All rights reserved. 4 Information Given by the Chemical Equation Balanced equation provides the relationship between the relative numbers of reacting molecules and product molecules 2 CO + O 2  2 CO 2 2 CO molecules react with 1 O 2 molecules to produce 2 CO 2 molecules

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 5 Information Given by the Chemical Equation Since the information given is relative: 2 CO + O 2  2 CO 2 200 CO molecules react with 100 O 2 molecules to produce 200 CO 2 molecules 2 billion CO molecules react with 1 billion O 2 molecules to produce 2 billion CO 2 molecules 2 moles CO molecules react with 1 mole O 2 molecules to produce 2 moles CO 2 molecules 12 moles CO molecules react with 6 moles O 2 molecules to produce 12 moles CO 2 molecules

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 6 Information Given by the Chemical Equation The coefficients in the balanced chemical equation shows the molecules and mole ratio of the reactants and products Since moles can be converted to masses, we can determine the mass ratio of the reactants and products as well

8 Information Given by the Chemical Equation 2 CO + O 2  2 CO 2 2 moles CO = 1mole O 2 = 2 moles CO 2 Since 1 mole of CO = 28.01 g, 1 mole O 2 = 32.00 g, and 1 mole CO 2 = 44.01 g 2(28.01) g CO + 1(32.00) g O 2 = 2(44.01) g CO 2

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 10 Mass Known Use Mole Ratio Moles Known Moles Unknown Mass unknown General Plan for Stoichiometry Calculations Obtain mole ratio from balanced chemical equation

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 11 ¬Write the balanced equation 2 CO + O 2  2 CO 2 ­Use the coefficients to find the mole relationship 2 moles CO = 1 mol O 2 = 2 moles CO 2 Example #1 Determine the Number of Moles of Carbon Monoxide required to react with 3.2 moles Oxygen, and determine the moles of Carbon Dioxide produced

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 12 ®Use dimensional analysis Example #1 Determine the Number of Moles of Carbon Monoxide required to react with 3.2 moles Oxygen, and determine the moles of Carbon Dioxide produced

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 13 ¬Write the balanced equation 2 CO + O 2  2 CO 2 ­Use the coefficients to find the mole relationship 2 moles CO = 1 mol O 2 = 2 moles CO 2 ®Determine the Molar Mass of each 1 mol CO = 28.01 g 1 mol O 2 = 32.00 g 1 mol CO 2 = 44.01 g Example #2 Determine the Number of grams of Carbon Monoxide required to react with 48.0 g Oxygen, and determine the mass of Carbon Dioxide produced

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 14 ¯Use the molar mass of the given quantity to convert it to moles °Use the mole relationship to convert the moles of the given quantity to the moles of the desired quantity Example #2 Determine the Number of grams of Carbon Monoxide required to react with 48.0 g Oxygen, and determine the mass of Carbon Dioxide produced

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 15 ±Use the molar mass of the desired quantity to convert the moles to mass Example #2 Determine the Number of grams of Carbon Monoxide required to react with 48.0 g Oxygen, and determine the mass of Carbon Dioxide produced

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 16 Calculate the number of moles of oxygen required to react exactly with 4.30 moles of propane, C 3 H 8, in the reaction described by the following equation…. C 3 H 8 + 5O 2  3CO 2 + 4H 2 O

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 17 Butane, also a fuel, reacts with oxygen to produce carbon dioxide and water. C 4 H 10 + O 2  CO 2 + H 2 O What mass of oxygen will be required to react exactly with 96.1 grams of butane?

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 18 Every day Examples: How many pairs of gloves can I make from 20 left gloves and 30 right gloves? If I have five eggs and 5 brownie mixes and each brownie mix needs two eggs, how many batches of brownies can I make? If I have 6 model car wheels, two bodies, 10 bumpers, 4 engines, how many model cars can I make?

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 19 Limiting Reactants R eactantsProducts 2 NO(g) + O 2 (g) 2 NO 2 (g) Limiting reactant = ___________ Excess reactant = ____________

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 20 Limiting and Excess Reactants A reactant which is completely consumed when a reaction is run to completion is called a limiting reactant A reactant which is not completely consumed in a reaction is called an excess reactant The maximum amount of a product that can be made when the limiting reactant is completely consumed is called the theoretical yield

Astronaut Sidney M. Gutierrez changes the lithium hydroxide canisters on Space Shuttle Columbia. Source: NASA

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 22 ¬Write the balanced equation 2 CO + O 2  2 CO 2 ­Use the coefficients to find the mole relationship 2 moles CO = 1 mol O 2 = 2 moles CO 2 Example #3 Determine the Number of Moles of Carbon Dioxide produced when 3.2 moles Oxygen reacts with 4.0 moles of Carbon Monoxide

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 23 Example #3 ®Use dimensional analysis to determine the number of moles of product produced from each reactant. Determine the Number of Moles of Carbon Dioxide produced when 3.2 moles Oxygen reacts with 4.0 moles of Carbon Monoxide

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 24 ¯Compare the calculated number of moles of product for reactant A to the number of moles of product for reactant B ¯Whichever reactant produces the least amount of product, that reactant is the limiting reactant Example #3 Determine the Number of Moles of Carbon Dioxide produced when 3.2 moles Oxygen reacts with 4.0 moles of Carbon Monoxide

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 25 °Use the limiting reactant to determine the moles of product Example #3 Determine the Number of Moles of Carbon Dioxide produced when 3.2 moles Oxygen reacts with 4.0 moles of Carbon Monoxide

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 26 Example #4 Determine the Mass of Carbon Dioxide produced when 48.0 g of Oxygen reacts with 56.0 g of Carbon Monoxide ¬Write the balanced equation 2 CO + O 2  2 CO 2 ­Use the coefficients to find the mole relationship 2 moles CO = 1 mol O 2 = 2 moles CO 2 ®Determine the Molar Mass of each 1 mol CO = 28.01 g 1 mol O 2 = 32.00 g 1 mol CO 2 = 44.01 g

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 27 ¯Determine the moles of each reactant Example #4 Determine the Mass of Carbon Dioxide produced when 48.0 g of Oxygen reacts with 56.0 g of Carbon Monoxide

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 28 °Determine the number of moles of reactant A needed to react with reactant B Example #4 Determine the Mass of Carbon Dioxide produced when 48.0 g of Oxygen reacts with 56.0 g of Carbon Monoxide

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 29 ±Compare the calculated number of moles of reactant A to the number of moles given of reactant A –If the calculated moles is greater, then A is the Limiting Reactant; if the calculated moles is less, then A is the Excess Reactant –the calculated moles of O 2 (1.00 moles) is less than the given 1.50 moles, therefore O 2 is the excess reactant Example #4 Determine the Mass of Carbon Dioxide produced when 48.0 g of Oxygen reacts with 56.0 g of Carbon Monoxide

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 30 ²Use the limiting reactant to determine the moles of product, then the mass of product Example #4 Determine the Mass of Carbon Dioxide produced when 48.0 g of Oxygen reacts with 56.0 g of Carbon Monoxide

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 31 Making Popcorn If we started with 80 popcorn kernels and found only 72 of them popped. What is the percent yield of popcorn?

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 32 Percent Yield Most reactions do not go to completion The amount of product made in an experiment is called the actual yield The percentage of the theoretical yield that is actually made is called the percent yield Percent Yield = Actual Yield Theoretical Yield x 100%

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 33 ³Divide the actual yield by the theoretical yield, then multiply by 100% The actual yield of CO 2 is 72.0 g The theoretical yield of CO 2 is 88.0g Example #4a Determine the Mass of Carbon Dioxide produced when 48.0 g of Oxygen reacts with 56.0 g of Carbon Monoxide If 72.0 g of Carbon Dioxide is actually made, what is the Percentage Yield

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 34 In-Class Discussion Questions 2.What happens to the weight of an iron bar when it rusts? a)There is no change because mass is always conserved b)The weight increases c)The weight increases, but if the rust is scraped off, the bar has its original weight. d)The weight decreases Justify your choice and, for the choices you did not pick, explain what is wrong with them.

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 35 Pancake Recipe 1 cup flour 2 eggs ½ cup water ½ tsp baking powder Makes 5 pancakes If I have a new bag of flour, a new box of baking powder and a ½ dozen eggs, how many pancakes can I make?

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 36 1.Given: 454 g NH 4 NO 3 2.Want: mass of N 2 O and H 2 O 3.Balance the reaction: __NH 4 NO 3  __N 2 O + __H 2 O 4.Convert knowns to moles 5.Solve for moles of wanted (or what is to be found) 6.Convert from moles to grams. If 454 g of ammonium nitrate decomposes, how much dinitrogen oxide and water are formed?

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 37 How many grams of oxygen form when 8.91 g KClO 3 (s) decomposes? KClO 3 (s)  KCl(s) + O 2 (g)

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 38 PROBLEM: Mix 5.40 g of solid aluminum with 8.10 g of chlorine gas. What mass of Al 2 Cl 6 can form? Mass reactant Moles reactant Moles product Mass product Is there a limiting reagent?

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 39 PROBLEM: Mix 5.40 g of solid aluminum with 8.10 g of chlorine gas. What mass of Al 2 Cl 6 can form? 1.Given: 5.40 g Al and 8.10 g Cl 2 2.Want: mass of Al 2 Cl 6 3.Balance the reaction: __Al(s) + __Cl 2 (g)  __Al 2 Cl 6 (s) 4.Convert to moles 5.Decide which reactant is limiting

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 40 PROBLEM: 25.0 kg of nitrogen gas and 5.00 kg of hydrogen gas are mixed and reacted to form ammonia. How many grams of ammonia are produced? 1.Given: 25.0 kg N 2 and 5.00 kg H 2 2.Want: mass of NH 3 3.Balance the reaction: __N 2 (g) + __H 2 (g)  __NH 3 (g) 4.Convert to moles 5.Decide which reactant is limiting

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 41 PROBLEM: 25.0 kg of nitrogen gas and 5.00 kg of hydrogen gas are mixed and reacted to form ammonia. How many grams of ammonia are produced? 1.Given: 25.0 kg N 2 and 5.00 kg H 2 2.Want: mass of NH 3 3.Balance the reaction: __N 2 (g) + __H 2 (g)  __NH 3 (g) 4.Convert to moles 5.Decide which reactant is limiting

Copyright©2004 by Houghton Mifflin Company. All rights reserved. 42 PROBLEM: 25.0 kg of nitrogen gas and 5.00 kg of hydrogen gas are mixed and reacted to form ammonia. How many grams of ammonia are produced? How much N 2 is left over? –N 2 (g) + 3 H 2 (g)  2 NH 3 (g) –892 mol of N 2 and 2.48 x 10 3 mol H 2