1. Chemical Change Chapter 9
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

2. Section 9.1 Electrolytes and Solution Conductivity
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3. Goal 1
Distinguish among strong electrolytes, weak electrolytes, and nonelectrolytes.
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4. Electrical Conductivity
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5. A substance that, when dissolved in water,
Strong Electrolyte:
A substance that, when dissolved in water,
conducts electricity strongly
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6. A substance that, when dissolved in water,
Weak Electrolyte:
A substance that, when dissolved in water,
conducts electricity, but does so poorly
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7. A substance that, when dissolved in water,
Nonelectrolyte:
A substance that, when dissolved in water,
does not conduct electricity
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8. Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

9. Conducting solutions contain ions
The extent of conductivity is related
to the concentration of ions in the solution
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10. Section 9.2 Solutions of Ionic Compounds
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

11. Goal 2
Given the formula of an ionic compound (or its name), write the formula of the ions present when it is dissolved in water.
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

12. The ions are identified by separating the compound into its ions
When an ionic compound dissolves in water, its solution consists of water molecules and ions
The ions are identified by separating
the compound into its ions
NaCl(s)
Na+(aq) + Cl–(aq)
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13. Na+(aq) + Cl–(aq) NaCl(s)
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14. K2SO4(s) 2 K+(aq) + SO42–(aq)
Polyatomic ions are treated in the same way in writing the formulas of ions in solution
K2SO4(s) K+(aq) + SO42–(aq)
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15. Section 9.3 Strong and Weak Acids
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16. Goal 3
Explain why the solution of an acid may be a good conductor or a poor conductor of electricity.
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

17. Goal 4
Given the formula of a soluble acid (or its name), write the major and minor species present when it is dissolved in water.
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18. Acid:
Hydrogen-bearing molecular compound made up of nonmetal elements that reacts with water to form a hydrated hydrogen ion and an anion HX
H2O +
H3O+ + X–
>
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19. Acid solutions can be strong or weak
electrolytes, depending on the extent to
which the acid molecule ionizes in solution
Strong acid:
Ionizes almost completely
HSt(aq) H+(aq) + St–(aq)
Major species:
ions
Minor species:
molecules
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

20. HWe(aq) H+(aq) + We–(aq)
Weak acid:
Ionizes very slightly
HWe(aq) H+(aq) + We–(aq)
Major species:
molecules
Minor species:
ions
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

21. Strong and weak acids at the macroscopic and particulate levels
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

22. Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

23. Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

24. Seven Common Strong Acids
HNO3
H2SO4
Two Well-
Known Acids
HBr
HCl HI
Three Group
7A/17 Acids
HClO3
HClO4
Two Chlorine
Oxyacids
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

25. Identifying the Major Species in a Solution
Ions are the major species in the
solutions of two kinds of substances:
All soluble ionic compounds
The seven strong acids
Neutral molecules are the major species in solutions of everything else, primarily:
Weak acids
Weak bases
Water
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

26. Section 9.4 Net Ionic Equations: What They Are and How to Write Them
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27. Consider the reaction of solutions of
silver nitrate and sodium chloride
What is the particulate-level composition
of each solution before the reaction occurs?
Silver nitrate solution:
Silver ions, Ag+(aq)
Nitrate ions, NO3–(aq)
Water molecules
Sodium chloride solution:
Sodium ions, Na+(aq)
Chloride ions, Cl–(aq)
Water molecules
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28. How are these represented in a conventional equation?
AgNO3(aq) + NaCl(aq)
The problem with this conventional representation is that it disguises the true composition of the solutions
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29. To avoid this misrepresentation, we can
write the formulas of the reactants as
they actually occur in solution
Ag+(aq) + NO3–(aq) + Na+(aq) + Cl–(aq)
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30. We can perform a similar analysis with the products of the reaction
Silver chloride precipitate:
Solid silver chloride, AgCl(s)
Sodium nitrate solution:
Sodium ions, Na+(aq)
Nitrate ions, NO3–(aq)
Water molecules
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

31. Conventional representation of products:
AgCl(s) + NaNO3(aq)
Products as they actually occur:
AgCl(s) + Na+(aq) + NO3–(aq)
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

32. Combining reactants and products:
AgNO3(aq) + NaCl(aq)
AgCl(s) + NaNO3(aq)
This is the conventional equation
It is good for stoichiometry problems
but lacks in revealing what really
happens in solution
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

33. Writing actual reactants and products:
AgCl(s) + Na+(aq) + NO3–(aq)
Ag+(aq) + NO3–(aq) + Na+(aq) + Cl–(aq)
This is the total ionic equation
It represents each species
as it actually occurs in solution
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

34. Note that some species appear as both reactant and product in the
total ionic equation:
Ag+(aq) + NO3–(aq) + Na+(aq) + Cl–(aq)
AgCl(s) + Na+(aq) + NO3–(aq)
NO3–(aq) is both reactant and product;
Na+(aq) is both reactant and product
Neither ion undergoes a chemical change
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

35. If we eliminate these non-reacting spectator ions,
Ag+(aq) + NO3–(aq) + Na+(aq) + Cl–(aq)
AgCl(s) + Na+(aq) + NO3–(aq)
What remains is the net ionic equation:
Ag+(aq) + Cl–(aq)
AgCl(s)
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

36. A net ionic equation describes what happens in a chemical change
Aqueous silver ion reacts with
aqueous chloride ion
to yield solid silver chloride
A net ionic equation ignores
non-reacting species:
Sodium ion
Nitrate ion
Water molecules
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

37. How to write a net ionic equation
Procedure:
How to write a net ionic equation
1. Write the conventional equation.
Include state symbols.
2. Write the total ionic equation.
Solids, liquids, and gases do not ionize.
Aqueous compounds may ionize:
A. Ionic compounds and strong acids ionize
B. Weak acids do not ionize
3. Write the net ionic equation.
Eliminate the spectators.
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

38. Section 9.7 Double-Replacement Precipitation Reactions
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

39. Goal 7
Predict whether a precipitate will form when known solutions are combined; if a precipitate forms, write the net ionic equation. (Reference to a solubility table or solubility rules may or may not be allowed.)
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

40. Goal 8
Given the product of a precipitation reaction, write the net ionic equation.
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

41. Precipitation Reactions
Double-Replacement
Precipitation Reactions
Reactants:
Reaction type:
Equation type:
Products:
Solutions of two ionic compounds or a solution of an ionic compound and an acid solution
Double-replacement precipitation
AX + BY AY + BX
Precipitate of ionic compound and
second ionic compound or acid
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

42. Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

43. Example:
Calcium nitrate and potassium sulfate solutions are combined. Write the net ionic equation.
Ca(NO3)2(aq) K2SO4(aq)
CaSO4( ) KNO3( ) 2
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

44. Conventional equation:
Ca(NO3)2(aq) K2SO4(aq)
CaSO4(s) KNO3(aq) 2
Total ionic equation:
Ca2+(aq) + 2 NO3–(aq) + 2 K+(aq) + SO42–(aq)
CaSO4(s) + 2 K+(aq) + 2 NO3–(aq)
Net ionic equation:
Ca2+(aq) + SO42–(aq)
CaSO4(s)
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45. Section 9.8 Double-Replacement Molecule-Formation Reactions
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46. Goal 9
Given reactants that yield a molecular product, write the net ionic equation.
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

47. Ion Combinations That Form Molecules
The reaction of an acid often leads to an ion combination that yields a molecular product, typically
water or a weak acid
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

48. Neutralization Reactions
Double-Replacement
Neutralization Reactions
Reactants:
Reaction type:
Equation type:
Products:
Acid (HX) and
a hydroxide base (MOH)
Double-replacement neutralization
HX + MOH H2O + HX
Water and a salt (MX)
(an ionic compound)
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

49. Write the net ionic equation for
Example:
Write the net ionic equation for
the reaction of solutions of hydrobromic acid
and sodium benzoate (benzoate ion, C7H5O2–).
Conventional equation:
HBr(aq) + NaC7H5O2(aq)
HC7H5O2(aq) + NaBr(aq)
HC7H5O2 is a weak acid
NaBr: Group 1A salts are soluble
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50. Conventional equation:
HBr(aq) + NaC7H5O2(aq)
HC7H5O2(aq) + NaBr(aq)
Total ionic equation:
H+(aq) + Br–(aq) + Na+(aq) + C7H5O2–(aq)
HC7H5O2(aq) + Na+(aq) + Br–(aq)
Net ionic equation:
H+(aq) + C7H5O2–(aq)
HC7H5O2(aq)
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51. Section 9.9 Double-Replacement Reactions That Form Unstable Products
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52. Goal 10
Given reactants that form H2CO3, H2SO3, or “NH4OH” by ion combination, write the net ionic equation for the reaction.
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53. Three common unstable products:
H2CO3(aq) H2O(l) + CO2(g)
H2SO3(aq) H2O(l) + SO2(aq)
“NH4OH” NH3(aq) + H2O(l)
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

54. Write the net ionic equation for the
Example:
Write the net ionic equation for the
reaction that occurs when hydrochloric acid
and sodium sulfite solutions are combined.
Conventional equation: 2
HCl(aq) + Na2SO3(aq)
H2SO3( ) + NaCl( ) aq
H2O(l) + SO2(aq)
Group 1A salts are soluble
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.

55. Conventional equation: 2 HCl(aq) + Na2SO3(aq)
H2O(l) + SO2(aq) + 2 NaCl(aq)
Total ionic equation:
2 H+(aq) + 2 Cl–(aq) + 2 Na+(aq) + SO32–(aq)
H2O(l) + SO2(aq) + 2 Na+(aq) + 2 Cl–(aq)
Net ionic equation:
2 H+(aq) + SO32–(aq)
H2O(l) + SO2(aq)
Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007 Brooks/Cole, a part of the Thomson Corporation.