Presentation on theme: "Limiting Reactants and Percent Yield"— Presentation transcript:
1Limiting Reactants and Percent Yield Chapter 9Limiting Reactantsand Percent Yield
2A. Limiting Reactant1. If you are given one dozen loaves of bread, a gallon of mustard, and three pieces of ham, how many ham sandwiches can you make?2. The limiting reactant is the reactant you run out of first.3. The excess reactant is the one you have left over.
34. The limiting reactant determines how much product you can make 5. What is the limiting reactant of your sandwich supplies?ham6. What is the excess reactant of your sandwich supplies?gallon of mustard
42. The one that makes the least product is the limiting reagent. B. How do you find out?1. Do two stoichiometry problems.2. The one that makes the least product is the limiting reagent.3. For exampleCopper reacts with sulfur to form copper ( I ) sulfide. If 10.6 g of copper reacts with 3.83 g S how much product will be formed?
5Cu is Limiting Reactant If 10.6 g of copper reacts with 3.83 g S. How many grams of product will be formed?2Cu + S ® Cu2SCu is Limiting Reactant1 mol Cu1 mol Cu2Sg Cu2S10.6 g Cu63.55g Cu2 mol Cu1 mol Cu2S= 13.3 g Cu2S= 13.3 g Cu2S1 mol S1 mol Cu2Sg Cu2S3.83 g S32.06g S1 mol S1 mol Cu2S= 19.0 g Cu2S
6C. Clarify 1. Limiting Reactant used up in a reaction determines the amount of product2. Excess Reactantadded to ensure that the other reactant is completely used upcheaper & easier to recycle
73. Example a. Available Ingredients 4 slices of bread 1 jar of peanut butter1/2 jar of jellyb. Limiting Reactantbreadc. Excess Reactantspeanut butter and jelly
8E. Calculating Limiting Reactants 1. Write a balanced equation.2. For each reactant, calculate the amount of product formed.3. Smaller answer indicates:limiting reactant4. Do Stoichiometry!
97. Still another exampleIf 10.3 g of aluminum are reacted with 51.7 g of CuSO4 how much copper will be produced?How much excess reagent will remain?Al CuSO4 -> Al2(SO4)3 + CuBalanced?2 Al CuSO4 -> Al2(SO4)3 + 3Cu
13A. Percent Yield1. The amount of product made in a chemical reaction.2. There are three types:a. Actual yield- what you get in the lab when the chemicals are mixedb. Theoretical yield- what the balanced equation tells what should be made
14c. Percent yield =Actual Theoretical3. DetailsPercent yield tells us how “efficient” a reaction is.Percent yield can not be bigger than 100 %.X 100%
16B. Example 16.78 g of copper is produced when 3.92 g of Al are reacted with excess copper (II) sulfate.2Al + 3 CuSO4 ® Al2(SO4)3 + 3CuWhat is the actual yield?What is the theoretical yield?What is the percent yield?
172Al + 3 CuSO4 ® Al2(SO4)3 + 3CuActual yield? 6.78gWhy? “cause it told me already!!!!Theoretical yield?Stoichiometry!!!!3.92g Al1mol Al3 mol Cu63.55g Cu26.98g Al1 mol Cu2mol Al= 13.85g Cu
18So, Theoretical yield is 13.85g Cu What is percent yield?Actual yieldTheoretical yield6.87g Cu13.85g CuX100%X100%= 48.95%
19Example 2When 45.8 g of K2CO3 react with excess HCl, 46.3 g of KCl are formed. Calculate the theoretical and % yields of KCl.K2CO3 + 2HCl 2KCl + H2O + CO245.8 g? gactual: 46.3 g
20K2CO3 + 2HCl 2KCl + H2O + CO2 45.8 g ? g actual: 46.3 g Theoretical Yield:1 molK2CO3g45.8 gK2CO32 molKCl1 molK2CO374.55g KCl1 molKCl= 49.4g KCl
22Yet another exampleIf 36.8g of C6H6 react with excess of Cl2And the actual yield of C6H5Cl is 38.8g, what is the percent yield?1st find theoretical yield of C6H5Cl1 mol C6H61mol C6H5Cl112.5g C6H5Cl36.8g C6H61mol C6H678.06g C6H61mol C6H5Cl= 53.03g C6H5Cl