 # CHAPTER 4 Stoichiometry. 2 Calculations Based on Chemical Equations How many CO molecules are required to react with 25 molecules of Fe 2 O 3 ?

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CHAPTER 4 Stoichiometry

2 Calculations Based on Chemical Equations How many CO molecules are required to react with 25 molecules of Fe 2 O 3 ?

3 Calculations Based on Chemical Equations What mass of CO is required to react with 146 g of iron (III) oxide?

4 Calculations Based on Chemical Equations What mass of carbon dioxide can be produced by the reaction of 0.540 mole of iron (III) oxide with carbon monoxide?

5 Calculations Based on Chemical Equations How many iron atoms can be produced by the reaction of 2.50 x 10 5 molecules of iron (III) oxide with excess carbon monoxide?

6 Calculations Based on Chemical Equations What mass of iron (III) oxide reacted with carbon monoxide if the carbon dioxide produced by the reaction had a mass of 8.65 grams? You do it!

7 Limiting Reactant Concept The reagent consumed first is the limiting reactant (or limited reagent) –-A chemical reaction proceeds forward according to the stoichiometry of the reaction until one (or both) reactants are consumed

8 Limiting Reactant Concept Kitchen example of limiting reactant concept: 1 packet of muffin mix + 2 eggs + 1 cup of milk  makes 12 muffins

9 Limiting Reactant Concept Mix PacketsEggsMilk 11 dozen1 gallon limited by the muffin mix 21 dozen1 gallon 31 dozen1 gallon 41 dozen1 gallon 51 dozen1 gallon 61 dozen1 gallon 71 dozen1 gallon limited by the amount of eggs 1 packet of muffin mix + 2 eggs + 1 cup of milk 12 muffins

10 Limiting Reactant Concept Suppose a box contains 87 bolts, 110 washers, and 99 nuts. How many sets, each consisting of one bolt, two washers, and one nut, can you construct from the contents of one box?

11 Limiting Reactant Concept How much sulfur dioxide can be produced by the reaction of 95.6 g of carbon disulfide with 1.10 x10 2 g of oxygen? Which is limiting reactant? What is maximum mass of sulfur dioxide that can be produced?

12 Percent Yield Theoretical yield is calculated by assuming that the reaction goes to completion –-Determined from a limiting reactant calculation Actual yield is the amount of a specified pure product made from the reactants –-In the laboratory, this is the amount of product that is formed in your beaker, after it is purified and dried Percent yield indicates how much of the product is obtained from the reaction

13 Percent Yield A 10.0 g sample of ethanol, C 2 H 5 OH, was boiled with excess acetic acid, CH 3 COOH, to produce 14.8 g of ethyl acetate, CH 3 COOC 2 H 5. What is the percent yield? 2. Calculate the percent yield

14 Types of Solutions

15 Concentrations of Solutions Common unit of concentration: = g solute MW solute liters solution

16 Solution Preparation Making a 1 M solution of sodium chloride Then add addition water until the 1.0 L mark is reached

17 Concentrations of Solutions Calculate the molarity of a solution that contains 12.5 g of sulfuric acid in 1.75 L of solution.

18 Concentrations of Solutions Determine the mass of calcium nitrate required to prepare 3.50 L of 0.800 M Ca(NO 3 ) 2. You do it!

19 Diluting a Solution A known amount of solvent is added to a known concentration and known amount of solution -number of moles of solute in the two solutions (concentrated and dilute) remains constant -mathematical relationship: M 1 V 1 = M 2 V 2 -Note: appropriate for dilutions, but not for chemical reactions

20 Diluting a Solution If 10.0 mL of 12.0 M HCl is added to enough water to give 100. mL of solution, what is the concentration of the solution?

21 Diluting a Solution What volume of 18.0 M sulfuric acid is required to make 2.50 L of a 2.40 M sulfuric acid solution?

22 Solutions in Chemical Reactions -chemical reactions are most often performed by using solutions of the reactants -Combine the concepts of molarity and stoichiometry

23 Solutions in Chemical Reactions What volume of 0.500 M BaCl 2 is required to completely react with 4.32 g of Na 2 SO 4 ?

24 Solutions in Chemical Reactions What volume of 0.200 M NaOH will react with 50.0 mL 0f 0.200 M aluminum nitrate, Al(NO 3 ) 3 ?

25 Titrations A method of determining the concentration of an unknown solution by reacting it with a known amount and concentration of a standard solution Standard solution: solution whose concentration has been determined using a primary standard by standardization Primary standard: chemical compound which can be used to accurately determine the concentration of another solution  Examples: include KHP and sodium carbonate

26 Primary Standard Potassium hydrogen phthalate (KHP) –molar mass of 204.2 g/mol.

27 Titrations Standardization: process in which the concentration of the standard solution is determined from the primary standard Indicator: substance that exists in different forms with different colors depending on the concentration of the H + in solution Examples: phenolphthalein and bromothymol blue. Equivalence point: point at which stoichiometrically equivalent amounts of the acid (H + ) and base (OH - ) have reacted End point: point at which the indicator changes color and the titration is complete

28 Titration Calculate the molarity of a NaOH solution if 27.3 mL of it reacts with 0.4084 g of KHP. KHP(aq) + NaOH(aq)  NaKP(aq) + H 2 O(l)

29 Titrations What is the molarity of a KOH solution if 38.7 mL of the KOH solution is required to react with 43.2 mL of 0.223 M HCl? KOH(aq) + HCl(aq) H 2 O(l) + KCl(aq)

30 Titrations What is the molarity of a barium hydroxide solution if 44.1 mL of 0.103 M HCl is required to react with 38.3 mL of the Ba(OH) 2 solution?

31 Titrations On Your Own Calculate the molarity of a sulfuric acid solution if 23.2 mL of it reacts with 0.212 g of Na 2 CO 3. H 2 SO 4 (aq) + Na 2 CO 3 (aq)  Na 2 SO 4 (aq) + H 2 O(l) + CO 2 (g)

32 Transmittance and Absorption Spectrum Transmittance (T): ratio of the amount of light that passes through a sample relative to the initial amount of light entering the sample Absorbance (A) = -log T = -log (P/P o ) Beer-Lambert Law (Beer’s Law): A =  bc

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