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Stoichiometry Limiting Reactions and Percentage Yield.

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Presentation on theme: "Stoichiometry Limiting Reactions and Percentage Yield."— Presentation transcript:

1 Stoichiometry Limiting Reactions and Percentage Yield

2 Stoichiometry  Objectives  Describe a method for determining which of two reactants is a limiting reactant  Calculate the amount in moles or mass in grams of a product, given the amounts in moles or masses in grams of two reactants, one of which is in excess  Distinguish between theoretical yield, actual yield, and percentage yield  Calculate percentage yield, given the actual yield and quantity of a reactant

3 Stoichiometry  Limiting Reactions  The limiting reactant is the reactant that limits the amount of the other reactant that can combine and the amount of product that can form in a chemical reaction  The excess reactant is the substance that is not used up completely in a reaction

4 Stoichiometry  Limiting Reactants  Sample Problem  Silicon dioxide (quartz) is usually quite unreactive but reacts readily with hydrogen fluoride according to the following equation  If 6.0 mol HF is added to 4.5 mol SiO 2, which is the limiting reactant? SiO 2 (s) + 4HF(g) → SiF 4 (g) + 2H 2 O(l)

5  Limiting Reactants  Sample Problem Solution  Given: amount of HF = 6.0 mol amount of SiO 2 = 4.5 mol  Unknown: limiting reactant Stoichiometry

6  Limiting Reactants  Sample Problem Solution Stoichiometry HF is the limiting reactant.

7 Stoichiometry  Percentage Yield  The theoretical yield is the maximum amount of product that can be produced from a given amount of reactant  The actual yield of a product is the measured amount of that product obtained from a reaction  The percentage yield is the ratio of the actual yield to the theoretical yield, multiplied by 100

8 Stoichiometry  Percentage Yield  Sample Problem  Chlorobenzene, C 6 H 5 Cl, is used in the production of many important chemicals, such as aspirin, dyes, and disinfectants. One industrial method of preparing chlorobenzene is to react benzene, C 6 H 6, with chlorine, as represented by the following equation  When 36.8 g C 6 H 6 react with an excess of Cl 2, the actual yield of C 6 H 5 Cl is 38.8 g.  What is the percentage yield of C 6 H 5 Cl? C 6 H 6 (l) + Cl 2 (g) → C 6 H 5 Cl(l) + HCl(g)

9  Percentage Yield  Sample Problem Solution  Given: mass of C6H6 = 36.8 g mass of Cl2 = excess actual yield of C 6 H 5 Cl = 38.8 g  Unknown: percentage yield of C 6 H 5 Cl Theoretical Yield Stoichiometry

10  Percentage Yield  Sample Problem Solution Percentage Yield

11 Stoichiometry

12 Sodium carbonate reacts with nitric acid according to the following equation. Na 2 CO 3 (s) + 2HNO 3  2NaNO 3 + CO 2 + H 2 O How many moles of Na 2 CO 3 are required to produce g of NaNO 3 ? Stoichiometry

13 Phosphorus burns in air to produce a phosphorus oxide in the following reaction: 4P(s) + 5O 2 (g)  P 4 O 10 (s) What mass of phosphorus will be needed to produce 3.25 mol of P 4 O 10 ? Stoichiometry

14 Aluminum will react with sulfuric acid in the following reaction. 2Al(s) + 3H 2 SO 4 (l)  Al 2 (SO 4 ) 3 (aq) + 3H 2 (g) How many moles of H 2 SO 4 will react with 18 mol Al? Stoichiometry

15 In the commercial production of the element arsenic, arsenic(III) oxide is heated with carbon, which reduces the oxide to the metal according to the following equation: 2As 2 O 3 + 3C  3CO 2 +4As If 8.87 g of As 2 O 3 is used in the reaction and 5.33 g of As is produced, what is the percentage yield? Stoichiometry

16 A process by which zirconium metal can be produced from the mineral zirconium(IV) orthosilicate, ZrSiO 4, starts by reacting it with chlorine gas to form zirconium(IV) chloride. ZrSiO 4 + 2Cl 2  ZrCl 4 + SiO 2 + O 2 What mass of ZrCl 4 can be produced if 862 g of ZrSiO 4 and 950. g of Cl 2 are available? Stoichiometry

17 Calculate the mass of silver bromide produced from 22.5 g of silver nitrate in the following reaction: 2AgNO 3 (aq) + MgBr 2 (aq)  2AgBr(s) + Mg(NO 3 ) 2 (aq) Stoichiometry

18 Use the following equation for the oxidation of aluminum in the following problems. 4Al + 3O 2  2Al 2 O 3 Which reactant is limiting if 0.32 mol Al and 0.26 mol O 2 are available? Stoichiometry

19 Hydrogen peroxide breaks down, releasing oxygen, in the following reaction: 2H 2 O 2 (aq)  2H 2 O(l) + O 2 (g) What mass of oxygen is produced when mol of H 2 O 2 decomposes? Stoichiometry

20 Hydrogen is generated by passing hot steam over iron, which oxidizes to form Fe 3 O 4, in the following equation. 3Fe(s) + 4H 2 O(g)  4H 2 (g) + Fe 3 O 4 (s) If 625 g of Fe 3 O 4 is produced in the reaction, how many moles of hydrogen are produced at the same time? Stoichiometry

21 Aluminum oxidizes according to the following equation: 4Al + 3O 2  2Al 2 O 3 Powdered Al (0.048 mol) is placed into a container containing mol O 2. What is the limiting reactant? Stoichiometry


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