Chpt_04_LE_student

# Chpt_04_LE_student - Chemical Quantities and Aqueous...

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1 Chemical Quantities Chemical Quantities and Aqueous Reaction and Aqueous Reaction Chapter 4 Chapter 4 Reaction Reaction Stoichiometry Stoichiometry ± Stoichiometry : tells us quantitative mass relationships in a chemical reaction ± Reaction stoichiometry answers the questions: ± How much of each reactant is consumed in a chemical reaction? ± How much of each product is produced in a chemical reaction? ± the coefficients in a balanced chemical equation specify the relative amounts in moles of each of the substances involved in the reaction 2 C 8 H 18 ( g ) + 25 O 2 ( g ) 16 CO 2 ( g ) + 18 H 2 O( g ) ± the amounts of any other substance in a chemical reaction can be determined from the amount of just one substance Example: How much of CO 2 (in moles) can be made from 22.0 moles of C 8 H 18 in the combustion of C 8 H 18 ? LE_Chem102A_01_Fall 2008 (Chapter 4)

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2 Example: In the reaction given below, what mass of CS 2 can be generated by the complete reaction of 67.2 g of sulfur? Stoichiometry Stoichiometry and Mass Relationship and Mass Relationship CH 4 + 4S CS 2 + 2H 2 S g S mol CS 2 g CS 2 mol S Concept Plan: Stoichiometry Stoichiometry and Mass Relationship (Cont and Mass Relationship (Cont ’d) d) Concept Plan: Solution: Example: According to the following equation, how many milliliters of water are made in the combustion of 9.0 g of glucose? Density of water is 1.00 g/mL. C 6 H 12 O 6 ( s ) + 6 O 2 ( g ) 6 CO 2 ( g ) + 6 H 2 O( l ) g glucose mol water g of water mol glucose mL of water LE_Chem102A_01_Fall 2008 (Chapter 4)
Limiting Reactant, Theoretical Yield and % Yield Limiting Reactant, Theoretical Yield and % Yield ± for reactions with multiple reactants, it is likely that one of the reactants will be completely used before the others ± when this reactant is used up, the reaction stops and no more product is made ± the reactant that limits the amount of product is called the limiting reactant ± sometimes called the limiting reagent ± the limiting reactant gets completely consumed ± in general, makes the least amount of product ± the amount of product that can be made from the limiting reactant is called the theoretical yield ± many things can happen during the course of an experiment that cause the loss of product (things don’t always go as planned!) ± the amount of product that is made in a reaction is called the actual yield ± generally less than the theoretical yield, never more ! ± the efficiency of product recovery is generally given as the percent yield % 100 yield l theoretica yield actual Yield Percent × = Limiting Reactant in the Combustion of Methane Limiting Reactant in the Combustion of Methane ± The balanced equation for the combustion of methane implies that every 1 molecule of CH 4 reacts with 2 molecules of O 2 ± Suppose we have 5 molecules of CH 4 and 8 molecules of O 2 , which is the limiting reactant? LE_Chem102A_01_Fall 2008 (Chapter 4)

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Chpt_04_LE_student - Chemical Quantities and Aqueous...

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