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Limiting Reactions and Percentage Yield

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1 Limiting Reactions and Percentage Yield
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 SiO2, which is the limiting reactant? SiO2(s) + 4HF(g) → SiF4(g) + 2H2O(l)

5 Stoichiometry Limiting Reactants Sample Problem Solution
Given: amount of HF = 6.0 mol amount of SiO2 = 4.5 mol Unknown: limiting reactant

6 Stoichiometry Limiting Reactants Sample Problem Solution
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, C6H5Cl, 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, C6H6, with chlorine, as represented by the following equation When 36.8 g C6H6 react with an excess of Cl2, the actual yield of C6H5Cl is 38.8 g. What is the percentage yield of C6H5Cl? C6H6 (l) + Cl2(g) → C6H5Cl(l) + HCl(g)

9 Stoichiometry Percentage Yield Sample Problem Solution
Given: mass of C6H6 = 36.8 g mass of Cl2 = excess actual yield of C6H5Cl = 38.8 g Unknown: percentage yield of C6H5Cl Theoretical Yield

10 Stoichiometry Percentage Yield Sample Problem Solution

11 Stoichiometry

12 Stoichiometry Sodium carbonate reacts with nitric acid according to the following equation. Na2CO3(s) + 2HNO3  2NaNO3 + CO2 + H2O How many moles of Na2CO3 are required to produce g of NaNO3?

13 Stoichiometry Phosphorus burns in air to produce a phosphorus oxide in the following reaction: 4P(s) + 5O2(g)  P4O10(s) What mass of phosphorus will be needed to produce 3.25 mol of P4O10?

14 Stoichiometry Aluminum will react with sulfuric acid in the following reaction. 2Al(s) + 3H2SO4(l)  Al2(SO4)3(aq) + 3H2(g) How many moles of H2SO4 will react with 18 mol Al?

15 Stoichiometry 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: 2As2O3 + 3C  3CO2 +4As If 8.87 g of As2O3 is used in the reaction and 5.33 g of As is produced, what is the percentage yield?

16 Stoichiometry A process by which zirconium metal can be produced from the mineral zirconium(IV) orthosilicate, ZrSiO4, starts by reacting it with chlorine gas to form zirconium(IV) chloride. ZrSiO4 + 2Cl2  ZrCl4 + SiO2 + O2 What mass of ZrCl4 can be produced if 862 g of ZrSiO4 and 950. g of Cl2 are available?

17 Stoichiometry Calculate the mass of silver bromide produced from 22.5 g of silver nitrate in the following reaction: 2AgNO3(aq) + MgBr2(aq) 2AgBr(s) + Mg(NO3)2(aq)

18 Stoichiometry Use the following equation for the oxidation of aluminum in the following problems. 4Al + 3O2  2Al2O3 Which reactant is limiting if 0.32 mol Al and 0.26 mol O2 are available?

19 Stoichiometry Hydrogen peroxide breaks down, releasing oxygen, in the following reaction: 2H2O2(aq)  2H2O(l) + O2(g) What mass of oxygen is produced when mol of H2O2 decomposes?

20 Stoichiometry Hydrogen is generated by passing hot steam over iron, which oxidizes to form Fe3O4, in the following equation. 3Fe(s) + 4H2O(g)  4H2(g) + Fe3O4(s) If 625 g of Fe3O4 is produced in the reaction, how many moles of hydrogen are produced at the same time?

21 Stoichiometry Aluminum oxidizes according to the following equation:
4Al + 3O2  2Al2O3 Powdered Al (0.048 mol) is placed into a container containing mol O2. What is the limiting reactant?

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