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General ChemistryPrinciples and Modern Applications   Petrucci • Harwood • Herring             8th Edition   Chapter 5: In...
Contents5-1   The Nature of Aqueous Solutions5-2   Precipitation Reactions5-3   Acid-Base Reactions5-4   Oxidation-Reducti...
5.1 The Nature of Aqueous SolutionsSlide 3 of 43   General Chemistry: Chapter 5                                           ...
Electrolytes• Some solutes can  dissociate into ions.• Electric charge can be  carried.Slide 4 of 43   General Chemistry: ...
Types of Electrolytes  • Strong electrolyte dissociates completely.     – Good electrical conduction.  • Weak electrolyte ...
Representation of Electrolytes using          Chemical EquationsA strong electrolyte:        MgCl2(s) → Mg2+(aq) + 2 Cl-(a...
Notation for Concentration          MgCl2(s) → Mg2+(aq) + 2 Cl-(aq)                  In 0.0050 M MgCl2:                Sto...
Example 5-1Calculating Ion concentrations in a Solution of a StrongElectolyte.What are the aluminum and sulfate ion concen...
Example 5-1Aluminum Concentration:        0.0165 mol Al2(SO4)3     2 mol Al3+ [Al] =                      ×               ...
5-2 Precipitation Reactions• Soluble ions can combine  to form an insoluble  compound.• Precipitation occurs.             ...
Net Ionic EquationOverall Precipitation Reaction:        AgNO3(aq) +NaI (aq) → AgI(s) + NaNO3(aq)Complete ionic equation: ...
Solubility Rules• Compounds that are soluble:  – Alkali metal ion and ammonium ion salts      Li+, Na+, K+, Rb+, Cs+      ...
Solubility Rules   •Compounds that are mostly soluble:   – Chlorides, bromides and iodides                   Cl-, Br-, I- ...
Solubility Rules  •Compounds that are insoluble:  – Hydroxides and sulfides                         HO-, S2-      • Except...
5-3 Acid-Base Reactions• Latin acidus (sour)   – Sour taste• Arabic al-qali (ashes of certain plants)   – Bitter taste• Sv...
Acids• Acids provide H+ in aqueous solution.• Strong acids:            HCl(aq)   →   H+(aq) + Cl-(aq)• Weak acids:      CH...
Bases• Bases provide OH- in aqueous solution.• Strong bases:            NaOH(aq)   → Na+(aq) + OH-(aq)                    ...
Recognizing Acids and Bases.• Acids have ionizable hydrogen ions.   – CH3CO2H or HC2H3O2• Bases have OH- combined with a m...
More Acid-Base Reactions• Milk of magnesia                Mg(OH)2    Mg(OH)2(s) + 2 H+(aq) → Mg2+(aq) + 2 H2O(l)    Mg(OH)...
More Acid-Base Reactions• Limestone and marble.        CaCO3(s) + 2 H+(aq) → Ca2+(aq) + H2CO3(aq)             But: H2CO3(a...
Limestone and MarbleSlide 21 of 43   General Chemistry: Chapter 5                                            Prentice-Hall
Gas Forming ReactionsSlide 22 of 43   General Chemistry: Chapter 5                                            Prentice-Hall
5-4 Oxidation-Reduction: Some             General Principles• Hematite is converted to iron in a blast furnace.           ...
Oxidation State Changes• Assign oxidation states:           3+ 2-        2+ 2-        0           4+ 2-                   ...
Oxidation and Reduction• Oxidation   – O.S. of some element increases in the reaction.   – Electrons are on the right of t...
Zinc in Copper Sulfate           Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s)Slide 26 of 43    General Chemistry: Chapter 5        ...
Half-Reactions• Represent a reaction by two half-reactions. Oxidation:               Zn(s) → Zn2+(aq) + 2 e- Reduction:   ...
Balancing Oxidation-Reduction Equations • Few can be balanced by inspection. • Systematic approach required. • The Half-Re...
Example 5-6Balancing the Equation for a Redox Reaction in Acidic Solution.The reaction described below is used to determin...
Example 5-6Determine the oxidation states:      4+          7+          6+          2+      SO32-(aq) + MnO4-(aq) → SO42-(...
Example 5-6Balance O by adding H2O:           H2O(l) + SO32-(aq) → SO42-(aq) + 2 e-(aq)         5 e-(aq) +MnO4-(aq) → Mn2+...
Example 5-6Multiply the half-reactions to balance all e-:   5 H2O(l) + 5 SO32-(aq) → 5 SO42-(aq) + 10 e-(aq) + 10 H+(aq) 1...
Balancing in Acid• Write the equations for the half-reactions.   –   Balance all atoms except H and O.   –   Balance oxyge...
Balancing in Basic Solution• OH- appears instead of H+.• Treat the equation as if it were in acid.   – Then add OH- to eac...
5-6 Oxidizing and Reducing Agents.  • An oxidizing agent (oxidant ):      – Contains an element whose oxidation state     ...
RedoxSlide 36 of 43   General Chemistry: Chapter 5                                            Prentice-Hall
Example 5-8Identifying Oxidizing and Reducing Agents.Hydrogen peroxide, H2O2, is a versatile chemical. Its usesinclude ble...
Example 5-8 H2O2(aq) + 2 Fe2+(aq) + 2 H+ → 2 H2O(l) + 2 Fe3+(aq)                                     Iron is oxidized and ...
5-7 Stoichiometry of Reactions in     Aqueous Solutions: Titrations.• Titration   – Carefully controlled addition of one s...
IndicatorsSlide 40 of 43   General Chemistry: Chapter 5                                            Prentice-Hall
Example 5-10Standardizing a Solution for Use in Redox Titrations.A piece of iron wire weighing 0.1568 g is converted to Fe...
Example 5-10  5 Fe2+(aq) + MnO4-(aq) + 8 H+(aq) → 4 H2O(l) + 5 Fe3+(aq) + Mn2+(aq)Determine KMnO4 consumed in the reaction...
Chapter 5 Questions          1, 2, 3, 5, 6, 8, 14, 17,          19, 24, 27, 33, 37, 41,          43, 51, 53, 59, 68, 71,  ...
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  • Iron rusts Natural gas burns Represent chemical reactions by chemical equations. Relationship between reactants and products is STOICHIOMETRY Many reactions occur in solution-concentration uses the mole concept to describe solutions
  • A generalization is helpful: Essentially all soluble ionic compounds are strong electrolytes. Most molecular compounds are weak electrolytes or non-electrolytes
  • Strong – complete dissociation Weak – reversible
  • Strong acids completely ionize in solution Weak acids partially ionize in solution Compare to the electrolyte strengths.
  • Strong bases completely dissociate (or nearly so) Primarily hydroxides of group 1 and some group 2 metals Certain substances produce ions by reacting with water, not just dissolving in it. NH 4 is a weak base because the eaciton does not go to completion. MOST bases are weak bases
  • Ionizable protons are usually inidicated separately in a formula.
  • Equation 1 is reaction with strong acid Equation 2 is reaction with weak acid Note the characteristic formation of water.
  • This equation shows CO 3 2- acting as a base instead of OH-. Our definition must be expanded from simple Arrhenius theory (Bronsted-Lowry and Lewis)
  • Fe(2) is oxidized to Fe(3). Therefore peroxide is an oxidizing agent. Peroxide is reduced to water. Mn(7) is reduced to Mn(2). Therefore peroxide is a reducing agent. Peroxide is oxidized to molecular oxygenl.
  • Transcript of "Ch05"

    1. 1. General ChemistryPrinciples and Modern Applications Petrucci • Harwood • Herring 8th Edition Chapter 5: Introduction to Reactions in Aqueous Solutions Philip Dutton University of Windsor, Canada Prentice-Hall © 2002 Slide 1 of 43 General Chemistry: Chapter 5 Prentice-Hall
    2. 2. Contents5-1 The Nature of Aqueous Solutions5-2 Precipitation Reactions5-3 Acid-Base Reactions5-4 Oxidation-Reduction: Some General Principles5-5 Balancing Oxidation-Reduction Equations5-6 Oxidizing and Reducing Agents5-7 Stoichiometry of Reactions in Aqueous Solutions: Titrations Focus on Water TreatmentSlide 2 of 43 General Chemistry: Chapter 5 Prentice-Hall
    3. 3. 5.1 The Nature of Aqueous SolutionsSlide 3 of 43 General Chemistry: Chapter 5 Prentice-Hall
    4. 4. Electrolytes• Some solutes can dissociate into ions.• Electric charge can be carried.Slide 4 of 43 General Chemistry: Chapter 5 Prentice-Hall
    5. 5. Types of Electrolytes • Strong electrolyte dissociates completely. – Good electrical conduction. • Weak electrolyte partially dissociates. – Fair conductor of electricity. • Non-electrolyte does not dissociate. – Poor conductor of electricity.Slide 5 of 43 General Chemistry: Chapter 5 Prentice-Hall
    6. 6. Representation of Electrolytes using Chemical EquationsA strong electrolyte: MgCl2(s) → Mg2+(aq) + 2 Cl-(aq)A weak electrolyte: CH3CO2H(aq) ← CH3CO2-(aq) + H+(aq) →A non-electrolyte: CH3OH(aq) Slide 6 of 43 General Chemistry: Chapter 5 Prentice-Hall
    7. 7. Notation for Concentration MgCl2(s) → Mg2+(aq) + 2 Cl-(aq) In 0.0050 M MgCl2: Stoichiometry is important.[Mg2+] = 0.0050 M [Cl-] = 0.0100 M [MgCl2] = 0 MSlide 7 of 43 General Chemistry: Chapter 5 Prentice-Hall
    8. 8. Example 5-1Calculating Ion concentrations in a Solution of a StrongElectolyte.What are the aluminum and sulfate ion concentrations in0.0165 M Al2(SO4)3?.Balanced Chemical Equation: Al2(SO4)3 (s) → 2 Al3+(aq) + 3 SO42-(aq) Slide 8 of 43 General Chemistry: Chapter 5 Prentice-Hall
    9. 9. Example 5-1Aluminum Concentration: 0.0165 mol Al2(SO4)3 2 mol Al3+ [Al] = × = 0.0330 M Al3+ 1L 1 mol Al2(SO4)3Sulfate Concentration: 0.0165 mol Al2(SO4)3 3 mol SO42- [SO4 ] = 2- × = 0.0495 M SO42- 1L 1 mol Al2(SO4)3 Slide 9 of 43 General Chemistry: Chapter 5 Prentice-Hall
    10. 10. 5-2 Precipitation Reactions• Soluble ions can combine to form an insoluble compound.• Precipitation occurs. Ag+(aq) + Cl-(aq) → AgCl(s)Slide 10 of 43 General Chemistry: Chapter 5 Prentice-Hall
    11. 11. Net Ionic EquationOverall Precipitation Reaction: AgNO3(aq) +NaI (aq) → AgI(s) + NaNO3(aq)Complete ionic equation: Spectator ionsAg+(aq) + NO3-(aq) + Na+(aq) + I-(aq) → AgI(s) + Na+(aq) + NO3-(aq)Net ionic equation: Ag+(aq) + I-(aq) → AgI(s) Slide 11 of 43 General Chemistry: Chapter 5 Prentice-Hall
    12. 12. Solubility Rules• Compounds that are soluble: – Alkali metal ion and ammonium ion salts Li+, Na+, K+, Rb+, Cs+ NH4+ – Nitrates, perchlorates and acetates NO3- ClO4- CH3CO2- Slide 12 of 43 General Chemistry: Chapter 5 Prentice-Hall
    13. 13. Solubility Rules •Compounds that are mostly soluble: – Chlorides, bromides and iodides Cl-, Br-, I- • Except those of Pb2+, Ag+, and Hg22+. – Sulfates SO42- • Except those of Sr2+, Ba2+, Pb2+ and Hg22+. • Ca(SO4) is slightly soluble.Slide 13 of 43 General Chemistry: Chapter 5 Prentice-Hall
    14. 14. Solubility Rules •Compounds that are insoluble: – Hydroxides and sulfides HO-, S2- • Except alkali metal and ammonium salts • Sulfides of alkaline earths are soluble • Hydroxides of Sr2+ and Ca2+ are slightly soluble. – Carbonates and phosphates CO32-, PO43- • Except alkali metal and ammonium saltsSlide 14 of 43 General Chemistry: Chapter 5 Prentice-Hall
    15. 15. 5-3 Acid-Base Reactions• Latin acidus (sour) – Sour taste• Arabic al-qali (ashes of certain plants) – Bitter taste• Svante Arrhenius 1884 Acid-Base theory.Slide 15 of 43 General Chemistry: Chapter 5 Prentice-Hall
    16. 16. Acids• Acids provide H+ in aqueous solution.• Strong acids: HCl(aq) → H+(aq) + Cl-(aq)• Weak acids: CH3CO2H(aq) ← → H+(aq) + CH3CO2-(aq)Slide 16 of 43 General Chemistry: Chapter 5 Prentice-Hall
    17. 17. Bases• Bases provide OH- in aqueous solution.• Strong bases: NaOH(aq) → Na+(aq) + OH-(aq) H 2O• Weak bases: NH3(aq) + H2O(l) ← → OH-(aq) + NH4+(aq)Slide 17 of 43 General Chemistry: Chapter 5 Prentice-Hall
    18. 18. Recognizing Acids and Bases.• Acids have ionizable hydrogen ions. – CH3CO2H or HC2H3O2• Bases have OH- combined with a metal ion. KOH or are identified by chemical equations Na2CO3(s) + H2O(l)→ HCO3-(aq) + 2 Na+(aq) + OH-(aq) Slide 18 of 43 General Chemistry: Chapter 5 Prentice-Hall
    19. 19. More Acid-Base Reactions• Milk of magnesia Mg(OH)2 Mg(OH)2(s) + 2 H+(aq) → Mg2+(aq) + 2 H2O(l) Mg(OH)2(s) + 2 CH3CO2H(aq) → Mg2+(aq) + 2 CH3CO2-(aq) + 2 H2O(l)Slide 19 of 43 General Chemistry: Chapter 5 Prentice-Hall
    20. 20. More Acid-Base Reactions• Limestone and marble. CaCO3(s) + 2 H+(aq) → Ca2+(aq) + H2CO3(aq) But: H2CO3(aq) → H2O(l) + CO2(g) CaCO3(s) + 2 H+(aq) → Ca2+(aq) + H2O(l) + CO2(g)Slide 20 of 43 General Chemistry: Chapter 5 Prentice-Hall
    21. 21. Limestone and MarbleSlide 21 of 43 General Chemistry: Chapter 5 Prentice-Hall
    22. 22. Gas Forming ReactionsSlide 22 of 43 General Chemistry: Chapter 5 Prentice-Hall
    23. 23. 5-4 Oxidation-Reduction: Some General Principles• Hematite is converted to iron in a blast furnace. ∆ Fe2O3(s) + 3 CO(g) → 2 Fe(l) + 3 CO2(g)• Oxidation and reduction always occur together. Fe3+ is reduced to metallic iron. CO(g) is oxidized to carbon dioxide. Slide 23 of 43 General Chemistry: Chapter 5 Prentice-Hall
    24. 24. Oxidation State Changes• Assign oxidation states: 3+ 2- 2+ 2- 0 4+ 2- ∆ Fe2O3(s) + 3 CO(g) → 2 Fe(l) + 3 CO2(g) Fe3+ is reduced to metallic iron. CO(g) is oxidized to carbon dioxide. Slide 24 of 43 General Chemistry: Chapter 5 Prentice-Hall
    25. 25. Oxidation and Reduction• Oxidation – O.S. of some element increases in the reaction. – Electrons are on the right of the equation• Reduction – O.S. of some element decreases in the reaction. – Electrons are on the left of the equation.Slide 25 of 43 General Chemistry: Chapter 5 Prentice-Hall
    26. 26. Zinc in Copper Sulfate Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s)Slide 26 of 43 General Chemistry: Chapter 5 Prentice-Hall
    27. 27. Half-Reactions• Represent a reaction by two half-reactions. Oxidation: Zn(s) → Zn2+(aq) + 2 e- Reduction: Cu2+(aq) + 2 e- → Cu(s) Overall: Cu2+(aq) + Zn(s) → Cu(s) + Zn2+(aq) Slide 27 of 43 General Chemistry: Chapter 5 Prentice-Hall
    28. 28. Balancing Oxidation-Reduction Equations • Few can be balanced by inspection. • Systematic approach required. • The Half-Reaction (Ion-Electron) Method Slide 28 of 43 General Chemistry: Chapter 5 Prentice-Hall
    29. 29. Example 5-6Balancing the Equation for a Redox Reaction in Acidic Solution.The reaction described below is used to determine the sulfite ionconcentration present in wastewater from a papermaking plant.Write the balanced equation for this reaction in acidic solution. . SO32-(aq) + MnO4-(aq) → SO42-(aq) + Mn2+(aq) Slide 29 of 43 General Chemistry: Chapter 5 Prentice-Hall
    30. 30. Example 5-6Determine the oxidation states: 4+ 7+ 6+ 2+ SO32-(aq) + MnO4-(aq) → SO42-(aq) + Mn2+(aq)Write the half-reactions: SO32-(aq) → SO42-(aq) + 2 e-(aq) 5 e-(aq) +MnO4-(aq) → Mn2+(aq)Balance atoms other than H and O: Already balanced for elements. Slide 30 of 43 General Chemistry: Chapter 5 Prentice-Hall
    31. 31. Example 5-6Balance O by adding H2O: H2O(l) + SO32-(aq) → SO42-(aq) + 2 e-(aq) 5 e-(aq) +MnO4-(aq) → Mn2+(aq) + 4 H2O(l)Balance hydrogen by adding H+: H2O(l) + SO32-(aq) → SO42-(aq) + 2 e-(aq) + 2 H+(aq)8 H+(aq) + 5 e-(aq) +MnO4-(aq) → Mn2+(aq) + 4 H2O(l)Check that the charges are balanced: Add e- if necessary. Slide 31 of 43 General Chemistry: Chapter 5 Prentice-Hall
    32. 32. Example 5-6Multiply the half-reactions to balance all e-: 5 H2O(l) + 5 SO32-(aq) → 5 SO42-(aq) + 10 e-(aq) + 10 H+(aq) 16 H+(aq) + 10 e-(aq) + 2 MnO4-(aq) → 2 Mn2+(aq) + 8 H2O(l)Add both equations and simplify: 5 SO32-(aq) + 2 MnO4-(aq) + 6H+(aq) → 5 SO42-(aq) + 2 Mn2+(aq) + 3 H2O(l)Check the balance! Slide 32 of 43 General Chemistry: Chapter 5 Prentice-Hall
    33. 33. Balancing in Acid• Write the equations for the half-reactions. – Balance all atoms except H and O. – Balance oxygen using H2O. – Balance hydrogen using H+. – Balance charge using e-.• Equalize the number of electrons.• Add the half reactions.• Check the balance.Slide 33 of 43 General Chemistry: Chapter 5 Prentice-Hall
    34. 34. Balancing in Basic Solution• OH- appears instead of H+.• Treat the equation as if it were in acid. – Then add OH- to each side to neutralize H+. – Remove H2O appearing on both sides of equation.• Check the balance.Slide 34 of 43 General Chemistry: Chapter 5 Prentice-Hall
    35. 35. 5-6 Oxidizing and Reducing Agents. • An oxidizing agent (oxidant ): – Contains an element whose oxidation state decreases in a redox reaction • A reducing agent (reductant): – Contains an element whose oxidation state increases in a redox reaction.Slide 35 of 43 General Chemistry: Chapter 5 Prentice-Hall
    36. 36. RedoxSlide 36 of 43 General Chemistry: Chapter 5 Prentice-Hall
    37. 37. Example 5-8Identifying Oxidizing and Reducing Agents.Hydrogen peroxide, H2O2, is a versatile chemical. Its usesinclude bleaching wood pulp and fabrics and substituting forchlorine in water purification. One reason for its versatility isthat it can be either an oxidizing or a reducing agent. For thefollowing reactions, identify whether hydrogen peroxide is anoxidizing or reducing agent. Slide 37 of 43 General Chemistry: Chapter 5 Prentice-Hall
    38. 38. Example 5-8 H2O2(aq) + 2 Fe2+(aq) + 2 H+ → 2 H2O(l) + 2 Fe3+(aq) Iron is oxidized and peroxide is reduced. 5 H2O2(aq) + 2 MnO4-(aq) + 6 H+ → 8 H2O(l) + 2 Mn2+(aq) + 5 O2(g) Manganese is reduced and peroxide is oxidized. Slide 38 of 43 General Chemistry: Chapter 5 Prentice-Hall
    39. 39. 5-7 Stoichiometry of Reactions in Aqueous Solutions: Titrations.• Titration – Carefully controlled addition of one solution to another.• Equivalence Point – Both reactants have reacted completely.• Indicators – Substances which change colour near an equivalence point.Slide 39 of 43 General Chemistry: Chapter 5 Prentice-Hall
    40. 40. IndicatorsSlide 40 of 43 General Chemistry: Chapter 5 Prentice-Hall
    41. 41. Example 5-10Standardizing a Solution for Use in Redox Titrations.A piece of iron wire weighing 0.1568 g is converted to Fe2+(aq)and requires 26.42 mL of a KMnO4(aq) solution for its titration.What is the molarity of the KMnO4(aq)? 5 Fe2+(aq) + MnO4-(aq) + 8 H+(aq) → 4 H2O(l) + 5 Fe3+(aq) + Mn2+(aq) Slide 41 of 43 General Chemistry: Chapter 5 Prentice-Hall
    42. 42. Example 5-10 5 Fe2+(aq) + MnO4-(aq) + 8 H+(aq) → 4 H2O(l) + 5 Fe3+(aq) + Mn2+(aq)Determine KMnO4 consumed in the reaction: 1 mol Fe 1 mol Fe 2 + nH 2O = 0.1568 g Fe × × × 55.847 g Fe 1 mol Fe − 1 mol MnO4 1 mol KMnO4 × − = 5.615 × 10 − 4 mol KMnO4 5 mol Fe 2 + 1 mol MnO4Determine the concentration: 5.615 × 10 −4 mol KMnO4 [ KMnO4 ] = = 0.02140 M KMnO4 0.02624 L Slide 42 of 43 General Chemistry: Chapter 5 Prentice-Hall
    43. 43. Chapter 5 Questions 1, 2, 3, 5, 6, 8, 14, 17, 19, 24, 27, 33, 37, 41, 43, 51, 53, 59, 68, 71, 82, 96.Slide 43 of 43 General Chemistry: Chapter 5 Prentice-Hall
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