2Theoretical, Actual, and Percent Yield Theoretical yieldThe maximum amount of product, which is calculated using the balanced equation.Actual yieldThe amount of product obtained when the reaction takes place.Percent yieldThe ratio of actual yield to theoretical yield.percent yield = actual yield (g) x theoretical yield (g)
4Calculating Percent Yield You prepared cookie dough to make 5 dozen cookies.The phone rings and you answer. While you talk, a sheetof 12 cookies burn and you throw them out. The restof the cookies are okay. What is the percent yield ofedible cookies?Theoretical yield 60 cookies possibleActual yield cookies to eatPercent yield 48 cookies x 100 = 80% yield cookies
5Learning CheckWithout proper ventilation and limited oxygen, the reaction of carbon and oxygen produces carbon monoxide.2C(g) O2(g) CO(g)What is the percent yield if 40.0 g CO are produced when 30.0 g O2 are used?1) 25.0%2) 75.0%3) 76.2%
6Solution 3) 76.2 % yield theoretical yield of CO 30.0 g O2 x 1 mole O2 x 2 moles CO x g CO32.0 g O mole O mole CO= g CO (theoretical)percent yield40.0 g CO (actual) x 100 = % yield52.5 g CO (theoretical)
7Learning Check When N2 and 5.00 g H2 are mixed, the reaction produces 16.0 g NH3. What is the percent yield forthe reaction?N2(g) + 3H2(g) NH3(g)1) %2) %3) %
8Solution 2) 56.5 % N2(g) + 3H2(g) 2NH3(g) 2) %N2(g) + 3H2(g) NH3(g)5.00 g H2 x 1 mole H2 x 2 moles NH3 x 17.0 g NH32.02 g H moles H mole NH3= g NH3 (theoretical)Percent yield = g NH3 x 100 = %28.2 g NH3
9Limiting Reactant A limiting reactant in a chemical reaction is the substance thatIs used up first.Limits the amount of product that can form and stops the reaction.
12Example of An Everyday Limiting Reactant How many peanut butter sandwiches could be made from 8 slices of bread and 1 jar of peanut butter?With 8 slices of bread, only 4 sandwiches could be made. The bread is the limiting item.
13Example of An Everyday Limiting Reactant How many peanut butter sandwiches could be made from 8 slices bread and 1 tablespoon of peanut butter?With 1 tablespoon of peanut butter, only 1 sandwich could be made. The peanut butter is the limiting item.
15Limiting ReactantWhen 4.00 moles H2 is mixed with 2.00 moles Cl2,how many moles of HCl can form?H2(g) Cl(g) 2HCl (g)4.00 moles moles ??? molesCalculate the moles of product that each reactant, H2 and Cl2, could produce.The limiting reactant is the one that produces the smallest amount of product.
16Limiting Reactant HCl from H2 4.00 moles H2 x 2 moles HCl = moles HCl1 moles H2 (not possible)HCl from Cl22.00 moles Cl2 x 2 moles HCl = moles HCl1 mole Cl (smaller number of moles, Cl2 will be used up first)The limiting reactant is Cl2 because it is used up first. Thus Cl2 produces the smaller number of moles of HCl.
18Limiting Reactants Using Mass If 4.80 moles Ca are mixed with 2.00 moles N2, which is the limiting reactant?3Ca(s) + N2(g) Ca3N2(s)moles of Ca3N2 from Ca4.80 moles Ca x 1 mole Ca3N2 = 1.60 moles Ca3N moles Ca (Ca is used up)moles of Ca3N2 from N22.00 moles N2 x 1 mole Ca3N2 = moles Ca3N21 mole N (not possible)Ca is used up when 1.60 mole Ca3N2 forms.Thus, Ca is the limiting reactant.
19Limiting Reactants Using Mass Calculate the mass of water produced when 8.00 g H2and 24.0 g O2 react?2H2(g) + O2(g) H2O(l)
20Limiting Reactants Using Mass Moles H2O from H2:8.00 g H2 x 1 mole H2 x 2 moles H2O = 3.97 moles H2O2.02 g H moles H (not possible)Moles H2O from O2:24.0 g O2 x 1 mole O2 x 2 moles H2O = 1.50 moles H2O32.0 g O mole O O2 is limitingThe maximum amount of product is 1.50 moles H2O,which is converted to grams.1.50 moles H2O x 18.0 g H2O = 27.0 g H2O1 mole H2O