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Introductory Chemistry: A Foundation FIFTH EDITION by Steven S. Zumdahl University of Illinois
Copyright©2004 by houghton Mifflin Company. All rights reserved. 1

2. Reactions in Aqueous Solutions Unit 2 Section 31

3. Overview In Chapter 7, goals for students are to:
1. Learn about some of the factors that cause reactions to occur.
2. Learn to identify the solid that forms in a precipitation reaction.
3. Learn to describe reactions in solution by writing molecular, complete, ionic, and net ionic equations.
4. Learn the key characteristics of reactions between strong acids and strong bases.
5. Learn the general characteristics of reactions between metals and nonmetals.
6. Understand electron transfer as a driving force for a chemical reaction.
7. Learn various classification schemes for reactions.
8. Consider additional classes of chemical reactions.

4. Predicting Whether a Reaction Will Occur
Forces that drive a reaction
formation of a solid (precipitate)
formation of water
transfer of electrons
formation of a gas
when chemicals (dissolved in water) are mixed and one of these 4 things can occur, the reaction will generally happen 2

5. What happens when an ionic compound dissolves in water?
Ba(NO3)2 (aq) means barium nitrate has been dissolved in water
Note: barium nitrate contains Ba2+ ions and NO3- ions
When a solid containing ions is dissolved in water, the ions separate and move around
NO3-
NO3-
Ba2+
NO3-
NO3-
Ba2+

6. Dissociation
ionic compounds
metal + nonmetal (Type I & II)
metal + polyatomic anion
polyatomic cation + anion
Acids and Bases
when ionic compounds dissolve in water the anions and cations are separated from each other; this is called dissociation
we know that ionic compounds dissociate when they dissolve in water because the solution conducts electricity 4

7. Figure 7. 2: Electrical conductivity of aqueous solutions
Figure 7.2: Electrical conductivity of aqueous solutions. (a) Pure water does not conduct an electric current. (b) When an ionic compound is dissolved in water, current flows and the lamp lights.

8. Dissociation Cu(SO4)(aq) = Cu+2(aq) + SO42-(aq)
potassium chloride dissociates in water into potassium cations and chloride anions
KCl(aq) = K+ (aq) + Cl- (aq)
copper(II) sulfate dissociates in water into copper(II) cations and sulfate anions
Cu(SO4)(aq) = Cu+2(aq) + SO42-(aq) K+
Cl- K Cl
Cu+2
SO42- Cu
SO4 5

9. K2(SO4)(aq) = 2 K+ (aq) + SO42-(aq)
Dissociation
potassium sulfate dissociates in water into potassium cations and sulfate anions
K2(SO4)(aq) = 2 K+ (aq) + SO42-(aq) K+
SO42- K
SO4 6

10. Precipitation Reactions
in all precipitation reactions, the ions of one substance are exchanged with the ions of another substance when their aqueous solutions are mixed
At least one of the products formed is insoluble in water
KI(aq) + AgNO3(aq)  KNO3(aq) + AgIs K+ I-
Ag+
NO3- Ag I 3

11. Predicting the Formation of a Precipitate
How can you predict the formation of a precipitate in a double-replacement reaction?
The mixing of two solutions can sometimes result in the formation of an insoluble salt called a precipitate.
- We use solubility rules to determine which product is the precipitate
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12. Process for Predicting the Products of a Precipitation Reaction
Determine what ions each aqueous reactant has
Exchange Ions
(+) ion from one reactant with (-) ion from other
Balance Charges of combined ions to get formula of each product
Balance the Equation
count atoms
Determine Solubility of Each Product in Water
solubility rules
if product is insoluble or slightly soluble, it will precipitate 7

13. Solubility Rules for Ionic Compounds
Interpret Data
Solubility Rules for Ionic Compounds
Compounds
Solubility
Exceptions
Salts of alkali metals and ammonia
Soluble
Some lithium compounds
Nitrate salts and chlorate salts
Few exceptions
Sulfate salts
Compounds of Pb, Ag, Hg, Ba, Sr, and Ca
Chloride salts
Compounds of Ag and some compounds of Hg and Pb
Carbonates, phosphates, chromates, sulfides, and hydroxides
Most are insoluble
Compounds of the alkali metals and of ammonia
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14. Describing Reactions in Aqueous Solutions
AIM: Learn to describe reactions in solution by writing molecular, complete, ionic, and net ionic equations.

15. Molecular Equations KNO3(aq) + AgCl(s) KCl(aq) + AgNO3(aq) 
Describing Reactions in Aqueous Solutions
Molecular Equations
An equation showing the reactants and products in undissociated form
Identify as solid (s), gas (g), liquid (l) or dissolved (aq)
KCl(aq) + AgNO3(aq) 
KNO3(aq) + AgCl(s)

16. Describing Reactions in Aqueous Solutions
Ionic Equations
An equation that shows all dissolved substances as ions (except for weak electrolytes and nonelectrolytes)
K+(aq) + Cl-(aq) + Ag+ (aq) + NO3- (aq) K+ (aq) + NO3- (aq) + AgCl(s)

17. Cl- (aq) + Ag+ (aq) AgCl(s)
Net Ionic Equations
ions that are both reactants and products are called spectator ions
K+ (aq) + Cl- (aq) + Ag+(aq) + NO3- (aq) K+ (aq) + NO3- (aq) + AgCl(s)
an ionic equation in which the spectator ions are dropped is called a net ionic equation
Cl- (aq) + Ag+ (aq) AgCl(s) 10

18. Describing Reactions in Solution Precipitation
1.Write the molecular equation, ionic equation, and net ionic equation for the reaction below. Identify spectator ions.
Rubidium hydroxide (aq) reacts with calcium chloride (aq) to produce 

19. Describing Reactions in Solution Precipitation
1. Molecular equation (reactants and products as compounds)
2RbOH(aq) + CaCl2(aq)  Ca(OH)2(s) + 2RbCl(aq)
2. Complete ionic equation (all strong electrolytes shown as ions)
2Rb+(aq) + 2OH- (aq) + Ca+(aq) + 2Cl-(aq)  Ca(OH)2 (s) Rb+(aq) + 2Cl-(aq)

20. Describing Reactions in Solution (continued)
3. Net ionic equation (show only components that actually react)
Ca+(aq) + 2OH(aq)  Ca(OH)2 (s)
Rb+ and Cl are “spectator” ions.

22. Predicting the Formation of a Precipitate
Will a precipitate form when aqueous solutions of Na2CO3(aq) and Ba(NO3)2(aq) are mixed?
Na2CO3(aq) + Ba(NO3)2 (aq) →
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23. Molecular equation, complete ionic equation and net ionic equation

24. Molecular equation, complete ionic equation and net ionic equation

25. Write the Molecular, Complete Ionic, and Net ionic equations
1. Predict the products formed when aqueous solution of aluminum nitrate is mixed with sodium hydroxide solution. 2. Predict the products formed when a lead(II) nitrate solution is mixed with a sodium iodide solution

26. Problem 1
Predict the precipitate formed when aqueous solution of aluminum nitrate is mixed with sodium hydroxide solution.

27. Answer for Problem 1

28. Answer for Problem 1
Net Ionic Equation

29. Problem 2
Predict the precipitate formed when a lead(II) nitrate solution is mixed with a sodium iodide solution

30. Answer for Problem 2

31. Problem 2
Write the molecular equation, the complete ionic equation, and the net ionic equation when a lead(II) nitrate solution is mixed with a sodium iodide solution.

32. Answer for Problem 2 The molecular equation is
The complete ionic equation is

33. Answer for Problem 2
The net ionic equation is

34. Strong Electrolytes
Any compound that dissolves (dissociates) in water produces separated ions, the substance is called a strong electrolyte.
- Examples: KCl, CuSO4
electrolytes are substances whose aqueous solution is a conductor of electricity
in strong electrolytes, virtually all the molecules are dissociated into ions 11

35. Weak Electrolytes and Nonelectrolytes
in nonelectrolytes, none of the molecules are dissociated into ions
in weak electrolytes, a small percentage of the molecules are dissociated into ions 11

36. Video

37. Acids

38. Bases

39. Reactions that Form Water: Acids + Bases
Acids all contain H+ cations and an anion
Bases all contain OH- anions and a cation
when acids dissociate in water they release H+ ions and their anions
when bases dissociate in water they release OH- ions and their cations 12

40. https://prezi.com/z_o845wma1aw/acids-and-bases/

41. Strong acids and strong bases
They are called strong acids.
They are called strong bases.

42. Important Points about Strong Acids and Strong Bases
Six strong acids
HCl, HBr, HI, HNO3, H2SO4, HClO3
A strong acid is a substance that completely dissociates (ionizes) in water. (Each molecule breaks up into an H+ ion plus an anion.
Strong bases
metal hydroxides
NaOH and KOH

43. Important Points about Strong Acids and Strong Bases
In the reaction of a strong acid and a strong base, one product is always water and the other is always an ionic compound called a salt, which remains dissolved in the water. This salt can be obtained as a solid by evaporating the water.

44. acid + base salt + water
Acid-Base Reactions
in the reaction of an acid with a base, the H+ from the acid combines with the OH- from the base to make water
the cation from the base combines with the anion from the acid to make the salt
acid + base salt + water
H2SO4(aq) + Ca(OH)2(aq)  CaSO4(aq) + 2 H2O(l)
the net ionic equation for an Acid-Base reaction is always
H+ (aq) + OH- (aq)  H2O(l) 13

45. Example of acid-base reaction
NaOH + HCl 

46. End of Chapter 7