Unit 8~ Stoichiometry Most of your notebooks are NOT graded. Please make sure to leave them in the same stack (NEATLY) after taking notes for me to grade!

Vocabulary-Do these in your notebook  Actual Yield  Excess reactant  Limiting reactant  Mole ratio  Percent yield  Stoichiometry  Theoretical yield  Actual Yield  Excess reactant  Limiting reactant  Mole ratio  Percent yield  Stoichiometry  Theoretical yield

Reaction Stoichiometry  Greek for “measuring elements”  Involves the mass relationships between reactants and products in a chemical reaction.  Based on balanced chemical equations & the Law of Conservation of Mass  Greek for “measuring elements”  Involves the mass relationships between reactants and products in a chemical reaction.  Based on balanced chemical equations & the Law of Conservation of Mass

4Fe(s) + 3O 2 (g)   2Fe 2 O 3 (s)  Review:  Atom – smallest unit of an element  Example: Fe  Molecule – group of atoms joined covalently  ex. O 2  Formula Unit – group of atoms joined ionically  ex. Fe 2 O 3  Review:  Atom – smallest unit of an element  Example: Fe  Molecule – group of atoms joined covalently  ex. O 2  Formula Unit – group of atoms joined ionically  ex. Fe 2 O 3

4Fe(s) + 3O 2 (g)   2Fe 2 O 3 (s)  4 atoms of iron reacts with 3 molecules of oxygen to produce 2 formula units of iron (III) oxide.  Remember coefficients also represent the number of moles.  So…. 4 moles of iron reacts with 3 moles of oxygen to produce 2 moles of iron (III) oxide.  4 atoms of iron reacts with 3 molecules of oxygen to produce 2 formula units of iron (III) oxide.  Remember coefficients also represent the number of moles.  So…. 4 moles of iron reacts with 3 moles of oxygen to produce 2 moles of iron (III) oxide.

Mole Ratios  A conversion factor that relates the amounts in moles of any 2 substances involved in a chemical reaction  Use the coefficients in the equation  Each ratio can be expressed in 2 ways  A conversion factor that relates the amounts in moles of any 2 substances involved in a chemical reaction  Use the coefficients in the equation  Each ratio can be expressed in 2 ways

Mole Ratios Practice Determine all of the mole ratios in this equation:  2HCl + Mg  H 2 + MgCl 2  2 mol HCl / 1 mol Mg  2 mol HCl / 1 mol H 2  2 mol HCl / 1 mol MgCl 2  1 mol Mg / 1 mole H 2  Etc… Determine all of the mole ratios in this equation:  2HCl + Mg  H 2 + MgCl 2  2 mol HCl / 1 mol Mg  2 mol HCl / 1 mol H 2  2 mol HCl / 1 mol MgCl 2  1 mol Mg / 1 mole H 2  Etc…

CO Li(OH)  Li 2 CO 3 + H 2 O  1. Determine all of the mole ratios in equation above.  Write them down on a separate sheet of paper to turn in at the end of class for a grade.  You will be adding other answers to this paper as well  1. Determine all of the mole ratios in equation above.  Write them down on a separate sheet of paper to turn in at the end of class for a grade.  You will be adding other answers to this paper as well

Review Molar Mass  Mass in grams of 1 mole of any substance.  To calculate we must have the _______ _________ from the periodic table. 2. Calculate the Molar Mass of the following: (add this to your paper to turn in, this is review for you!) Al 2 O 3 CH 4 Al 2 (SO 4 ) 3  Mass in grams of 1 mole of any substance.  To calculate we must have the _______ _________ from the periodic table. 2. Calculate the Molar Mass of the following: (add this to your paper to turn in, this is review for you!) Al 2 O 3 CH 4 Al 2 (SO 4 ) 3

Stoichiometry ~ type 1: Converting Moles to Moles  Given substance is in Moles  Unknown substance is Moles  One conversion factor required  Given substance is in Moles  Unknown substance is Moles  One conversion factor required

Moles  Moles Practice CO LiOH  Li 2 CO 3 + H 2 O How many moles of Lithium hydroxide are required to react with 20 mol of CO 2 ? Given = 20 mol CO 2 Unknown = Li(OH) in moles CO LiOH  Li 2 CO 3 + H 2 O How many moles of Lithium hydroxide are required to react with 20 mol of CO 2 ? Given = 20 mol CO 2 Unknown = Li(OH) in moles 20 mol CO 2 2 mol Li(OH) 1 mol CO 2 X=

Type 2: Converting Moles to Grams  Given substance is in Moles  Unknown substance is Grams  2 Conversion factors required  Given substance is in Moles  Unknown substance is Grams  2 Conversion factors required

Moles  Grams Practice CO LiOH  Li 2 CO 3 + H 2 O How many grams of Lithium hydroxide are required to react with 20 mol of CO 2 ? Given = 20 mol CO 2 Unknown = Li(OH) in grams CO LiOH  Li 2 CO 3 + H 2 O How many grams of Lithium hydroxide are required to react with 20 mol of CO 2 ? Given = 20 mol CO 2 Unknown = Li(OH) in grams 20 mol CO 2 X 2 mol Li(OH) 1 mol CO 2 X 24g Li(OH)

Type 3: Converting Grams to Moles  Given substance is in Grams  Unknown substance is Moles  2 Conversion factors required  Given substance is in Grams  Unknown substance is Moles  2 Conversion factors required

Grams  Moles Practice CO LiOH  Li 2 CO 3 + H 2 O How many moles of Lithium hydroxide are required to react with 85 grams of CO 2 ? Given = 85 grams CO 2 Unknown = Li(OH) in moles CO LiOH  Li 2 CO 3 + H 2 O How many moles of Lithium hydroxide are required to react with 85 grams of CO 2 ? Given = 85 grams CO 2 Unknown = Li(OH) in moles 85g CO 2 X 1 44g X 2 mol Li(OH) 1 mol CO 2

Type 4: Converting Grams to Grams  Given substance is in Grams  Unknown substance is Grams  3 Conversion factors required  Given substance is in Grams  Unknown substance is Grams  3 Conversion factors required

Grams  Grams Practice CO LiOH  Li 2 CO 3 + H 2 O How many grams of Lithium hydroxide are required to react with 96 grams of CO 2 ? Given = 96 grams CO 2 Unknown = LiOH in grams CO LiOH  Li 2 CO 3 + H 2 O How many grams of Lithium hydroxide are required to react with 96 grams of CO 2 ? Given = 96 grams CO 2 Unknown = LiOH in grams 96g CO 2 X 1 44g X 2 mol Li(OH) 1 mol CO 2 X 24g =

Use this equation for #1-3 N 2 + 3H 2  2NH 3 1.How many moles of nitrogen (N 2 ) are required to produce 16 moles NH 3 ? 2.How many moles of hydrogen (H 2 ) are required to produce 96.5 grams of NH 3 ? 3.How many grams of NH 3 are produced from the reaction of 8 moles of nitrogen? N 2 + 3H 2  2NH 3 1.How many moles of nitrogen (N 2 ) are required to produce 16 moles NH 3 ? 2.How many moles of hydrogen (H 2 ) are required to produce 96.5 grams of NH 3 ? 3.How many grams of NH 3 are produced from the reaction of 8 moles of nitrogen?

Use this Equation for Questions 1-3 Cu 2 O + 2HCl  2CuCl + H 2 O 1.How many moles of CuCl are produced from 548 grams of Cu 2 O? 2.How many grams of HCl are required to react with 35 grams of Cu 2 O? 3.How many moles of CuCl are produced from 5 moles of HCl? 1.How many moles of CuCl are produced from 548 grams of Cu 2 O? 2.How many grams of HCl are required to react with 35 grams of Cu 2 O? 3.How many moles of CuCl are produced from 5 moles of HCl?

Reactants  Reactions are rarely carried out with exactly the required amounts of each reactant.  Limiting Reactant – the reactant that limits the amounts of the products that can form (It is used up first)  Excess Reactant – the substance that is not used up completely in a reaction.  Reactions are rarely carried out with exactly the required amounts of each reactant.  Limiting Reactant – the reactant that limits the amounts of the products that can form (It is used up first)  Excess Reactant – the substance that is not used up completely in a reaction.

Consider this...  If you are given one dozen loaves of bread, a gallon of mustard and three pieces of salami, how many salami sandwiches can you make? Now DECIDE:  What is the limiting reactant?  What is the excess reactant?  If you are given one dozen loaves of bread, a gallon of mustard and three pieces of salami, how many salami sandwiches can you make? Now DECIDE:  What is the limiting reactant?  What is the excess reactant?

Determining the Theoretical Yield & Limiting Reactant  You must do 2 stoichiometry problems.  Start each problem with one of the reactants.  The one that produces the least product (in grams) is the limiting reactant. EXAMPLE  Copper 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?  You must do 2 stoichiometry problems.  Start each problem with one of the reactants.  The one that produces the least product (in grams) is the limiting reactant. EXAMPLE  Copper 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?

 If 10.6 g of copper reacts with 3.83 g S. How many grams of product will be formed?  2Cu + S  Cu 2 S  If 10.6 g of copper reacts with 3.83 g S. How many grams of product will be formed?  2Cu + S  Cu 2 S 10.6 g Cu 63.55g Cu 1 mol Cu 2 mol Cu 1 mol Cu 2 S 1 mol Cu 2 S g Cu 2 S = 13.3 g Cu 2 S 3.83 g S 32.06g S 1 mol S 1 S 1 Cu 2 S 1 mol Cu 2 S g Cu 2 S = 19.0 g Cu 2 S = 13.3 g Cu 2 S Cu is Limiting Reagent

Percent Yields  The amount of product made in a chemical reaction. There are three types  Actual yield  Theoretical yield  Percent yield  The amount of product made in a chemical reaction. There are three types  Actual yield  Theoretical yield  Percent yield

 Actual yield- what you get in the lab when the chemicals are mixed (actual measured amount you get)  Theoretical yield- what the balanced equation tells you, you should make (max. amount that can be made given perfect conditions – involves calculations).  Percent yield – the ratio of actual yield to theoretical yield.  Percent yield  Percent yield = Actual x 100 = % Theoretical  Actual yield- what you get in the lab when the chemicals are mixed (actual measured amount you get)  Theoretical yield- what the balanced equation tells you, you should make (max. amount that can be made given perfect conditions – involves calculations).  Percent yield – the ratio of actual yield to theoretical yield.  Percent yield  Percent yield = Actual x 100 = % Theoretical

Percent Yield Cont.  Can never be more than 100%  First determine the limiting reactant, this will tell you the theoretical yield.  Actual yield will be given to you in the problem.  Then use the Equation: Percent yield Percent yield = Actual x 100 = % Theoretical  Can never be more than 100%  First determine the limiting reactant, this will tell you the theoretical yield.  Actual yield will be given to you in the problem.  Then use the Equation: Percent yield Percent yield = Actual x 100 = % Theoretical

Example Problem C 6 H 6 + Cl 2  C 6 H 5 Cl + HCl When 36.8 g of C 6 H 6 reacts with 11.5 g of Cl 2 what is the limiting reactant and theoretical yield? If the actual yield is of C 6 H 5 Cl is 12.0 g what is the percent yield of C 6 H 5 Cl? C 6 H 6 + Cl 2  C 6 H 5 Cl + HCl When 36.8 g of C 6 H 6 reacts with 11.5 g of Cl 2 what is the limiting reactant and theoretical yield? If the actual yield is of C 6 H 5 Cl is 12.0 g what is the percent yield of C 6 H 5 Cl?