7Chemical RatiosSubstances in a balanced equation are always in a given proportion to each other.1N2 + 3H2 2NH3The proportions can be written as ratios.
8Mole Ratios These proportions are called “mole ratios”. 1N2 + 3H2 2NH3For EveryThere are/isCreating ratio1N23H21mol N2/3mol H22NH3N2
9Mole RatiosWhat is the mole ratio found in the balanced equation below?N2O5 NO2 + O2
10The “Given”If 2 moles of N2O5 is reacted, how many moles of NO2 will be formed?There is always a given in a stoichiometry problem that includesA numeric value (2)A metric unit (moles)A substance (N2O5)
11Mole-Mole Calculation If 2 moles of N2O5 is reacted, how many moles of NO2 will be formed?1) 2 mol N2O5 x mole ratio (which one?)2) 2 mol N2O5 xmol N2O5 (cancel the given)3) 2 mol N2O5 x mol NO2 (write what you want)mol N2O5
12Mole-Mole Calculation 1- Balance the equation2- Write down your given3- Use conversion factors to convert moles(use the coefficients here)We call this the Heartof the equation
14Mole-Mole Calculations Coef mol_______________________mol givencoef mol unknowncoef mol given
15Mole-Mass Problem mol A 1 mol B How much (mass) B can be formed from a given number of moles of A?mol A x mol B x g B = g Bmol A mol B1) The mol-mol ratio comes from the equation2) The mol-mass ratio comes from the periodic table
16C3H8 + 5O2 3CO2 + 4H2O5.4 moles of propane (C3H8) is converted into how many moles of carbon dioxide?
184NH3 + 5O2 6H2O + 4NOHow many grams of H2O are produced if 1.9 mol of NH3 are combined with excess oxygen?
19Mass-Mole ProblemHow many moles of B can be formed from a given mass of A?g A x 1 mol A x mol B x = mol Bg A mol A1) The mol-mol ratio comes from the equation2) The mol-mass ratio comes from the periodic table
20Mass-Mole Calculations: mol given mol coef mol unknown__________________________________molar mass coef mol given(g)
21Fe2O3 + 3CO -> 2Fe + 3CO2How many grams of carbon dioxide are produced with 2 moles of iron (3) oxide?
22Mass-Mass ProblemHow much (mass) B can be formed from a given mass of A?g A x 1 mol A x mol B x g B = g Bg A mol A mol B1) The mol-mol ratio comes from the equation2) The mol-mass ratio comes from the periodic table
26Mole Ratios Limiting Reagent-LR % Yield Gas Stoichiometry
27Limiting ReagentLimiting reagent = a reactant that limits the amount of product that can be madeIt can also be thought of as a limiting ingredient
28Limiting Reagent Recipe: peanut butter and jelly sandwich 2Br + 3Pb + 2Je 1 Sa3 ingredients necessary to produce one sandwichCould any one of these runout before the other two?
29Excess Reagents Excess = there’s extra of this substance *the substance won’t run out*don’t include this reagent in the calculationIf you have 20 loaves of bread, 1 jar of peanut butter and 1 jar of jelly – which ingredient is in excess?
30Limiting ReagentTo determine the limiting reagent, more than one problem must be doneEx: You have 8 slices of bread and 9 T of peanut butter. Which is the limiting ingredient? (2Br + 3Pb + 2Je 1 Sa)8 Br x 1Sa = 4 Sa 9 Pb x 1Sa = 3 Sa2 Br Pb
31Limiting ReagentThe reactant that produces the smallest amount of product is the limiting reagent.8 Br x 1Sa = 4 Sa 9 Pb x 1Sa = 3 Sa2 Br PbLimiting reagentSmaller quantity
32Uses for Limiting Reactants Nutritional value of food for bodyConcentration of pollutants
33What to do (write these down): Balance equationConvert: 1-have to moles2-need to molesCompare have : needOne must be > or <ID the LRExcess compare your have : need
41% Yield Theoretical Yield = calculated mass of product Actual Yield = mass of product found in labPercent Yield = actual yield x 100%theoretical yield
42Percent YieldMethanol can be produced through the reaction of CO and H2 in the presence of a catalyst.CO(g) + 2H2(g) CH3OH(l)If 75.0 g of CO reacts to produce 68.4 g CH3OH, what is the percent yield of CH3OH?79.8%
43% YieldChlorobenzene, C6H5Cl is used in the production of many important chemicals, such as aspirin, dyes, and disinfectants.C6H6(l) + Cl2(g) C6H5Cl(s) + HCl(g)When 36.8 g of C6H6 react with an excess of Cl2, the actual yield of C6H5Cl is 38.8 g. What is the percent yield of C6H5Cl?73.2%
44% YieldAluminum reacts with excess copper (II) sulfate according to the reaction below. If 1.85 g of Al react and the percent yield of Cu is 56.6%, what mass of Cu is produced?Al(s) + CuSO4(aq) Al2(SO4)3(aq) + Cu(s)3.70 g
45Stoichiometry Ratios and Proportions Mole Ratios Limiting Reagent YieldGas Stoichiometry
46*This volume assumes standard temperature and pressure conditions Molar VolumeMolar volume = the space that one mole of ANY gas fills1 mole = *22.4 litersRemember: 1 L = 1000 mL*This volume assumes standard temperature and pressure conditions
47Molar Volume1) A quantity of gas has a volume of cm3. How many moles of gas are there?
48Molar Volume 2) Hydrogen sulfide occupies 278.2cm3. What is the mass of the hydrogen sulfide?
49Gas StoichiometryInstead of counting moles in a reaction, we can also count liters of a gas.1 liter of N2 reacts with 3 liters of H2 to produce 2 liters of NH3
50Gas StoichiometryWhat volume of water vapor will be formed when 8.2 L of H2 reacts with excess O2?2H2 (g) + O2 (g) 2H2O(g)Use a liter-liter ratio!
51Gas StoichiometryWhat volume of ammonia will form when 52.5 g of nitrogen reacts with excess hydrogen?gN2 mol N2 mol NH3 L NH3gN2 mol N2 L N2 L NH3