1. Chapter 5 Lecture Outline
Prepared by
Ashlyn Smith
Anderson University
Copyright © McGraw-Hill Education. Permission required for reproduction or display.

2. 5.3 Types of Reactions
The majority of chemical reactions fall into 6 categories:
combination
decomposition
single replacement
double replacement
oxidation and reduction (Section 5.4)
acid-base (Chapter 9)

3. 5.3 Types of Reactions B. Replacement Reactions
A double replacement reaction is a reaction in which two compounds exchange “parts”–atoms or ions—to form two new compounds.

4. 5.4 Oxidation and Reduction A. General Features
Oxidation is the loss of electrons from an atom.
Reduction is the gain of electrons by an atom.
Both processes occur together in a single reaction called an oxidation−reduction or redox reaction.
A redox reaction always has two components, one that is oxidized and one that is reduced.
A redox reaction involves the transfer of electrons from one element to another.

5. 5.4 Oxidation and Reduction A. General Features
Zn loses 2 e− to form Zn2+, so Zn is oxidized.
Cu2+ gains 2 e− to form Cu, so Cu2+ is reduced.

6. 5.4 Oxidation and Reduction A. General Features
Cu2+ gains 2 e−
Zn Cu2+
Zn Cu
Zn loses 2 e–
Each of these processes can be written as an
individual half reaction:
Oxidation half reaction: Zn
Zn e−
loss of e−
Reduction half reaction:
Cu e− Cu
gain of e−

7. 5.4 Oxidation and Reduction A. General Features
Zn Cu2+
Zn Cu
oxidized
reduced
A compound that is oxidized while causing another
compound to be reduced is called a reducing agent.
Zn acts as a reducing agent because it causes
Cu2+ to gain electrons and become reduced.

8. 5.4 Oxidation and Reduction A. General Features
Zn Cu2+
Zn Cu
oxidized
reduced
A compound that is reduced while causing another
compound to be oxidized is called an oxidizing agent.
Cu2+ acts as an oxidizing agent because it causes
Zn to lose electrons and become oxidized.

9. 5.4 Oxidation and Reduction A. General Features

10. 5. 4 Oxidation and Reduction B
5.4 Oxidation and Reduction B. Examples of Oxidation–Reduction Reactions
Iron Rusting
O gains e– and is reduced.
4 Fe(s) O2(g)
2 Fe2O3(s)
neutral Fe
neutral O
Fe3+
O2–
Fe loses e– and is oxidized.

11. 5. 4 Oxidation and Reduction B
5.4 Oxidation and Reduction B. Examples of Oxidation–Reduction Reactions
Zn MnO2
ZnO Mn2O3

12. Displacement of Copper by Zinc

13. Double Displacement Reactions
Two ionic compounds exchange ions.
May be followed by decomposition of one of the products to make a gas.
X ÅYq (aq) + A ÅBq (aq) ® XB + AY
Precipitation, acid–base, and gas evolving reactions are also double displacement reactions.

14. Predicting Whether a Reaction Will Occur in Aqueous Solution
“Forces” that drive a reaction:
Formation of a solid.
Formation of water.
Formation of a gas.
Transfer of electrons.
When chemicals (dissolved in water) are mixed and one of the above-noted forces occur, the reaction will generally happen.

15. Dissociation
Potassium iodide dissociates in water into potassium cations and iodide anions.
KI(aq) → K+1(aq) + I-1(aq)
Copper(II) sulfate dissociates in water into copper(II) cations and sulfate anions.
CuSO4(aq) → Cu+2(aq) + SO4-2(aq)
K+1
I-1 K I
SO4
SO4-2 Cu
Cu+2

16. When Will a Salt Dissolve?
A compound is soluble in a liquid if it dissolves in that liquid.
NaCl is soluble in water
A compound is insoluble if a significant amount does not dissolve in that liquid.
AgCl is insoluble in water.

17. Solubility Rules: Compounds that Are Generally Soluble in Water
Compounds containing the following ions are generally soluble
Exceptions
(when combined with ions on the left the compound is insoluble)
Li+, Na+, K+, NH4+
none
NO3–, C2H3O2–
Cl–, Br–, I–
Ag+, Hg22+, Pb2+
SO42–
Ca2+, Sr2+, Ba2+, Pb2+

18. Solubility Rules: Compounds that Are Generally Insoluble
Compounds containing the following ions are generally insoluble
Exceptions
(when combined with ions on the left the compound is soluble or slightly soluble)
OH–
Li+, Na+, K+, NH4+,
Ca2+, Sr2+, Ba2+
S2–
CO32–, PO43–
Li+, Na+, K+, NH4+

19. Determine if Each of the Following Is Soluble in Water
KOH
AgBr
CaCl2
Pb(NO3)2
PbSO4

20. Determine if Each of the Following Is Soluble in Water, Continued
KOH Soluble, because the cation is K+.
AgBr Insoluble, even though most compounds with Br− are soluble, this is an exception.
CaCl2 Soluble, most compounds with Cl− are soluble.
Pb(NO3)2 Soluble, because the anion is NO3−.
PbSO4 Insoluble, even though most compounds with SO42− are soluble, this is an exception.

21. Precipitation Reactions
Many reactions are done by mixing aqueous solutions of electrolytes together.
The cations and anions exchange
If the new compound is insoluble in water, it will “precipitate out”

22. Precipitation Reactions
2 KI(aq) + Pb(NO3)2(aq)  2 KNO3(aq) + PbI2(s)

23. Precipitation Reactions, Continued
2 KI(aq) + Pb(NO3)2(aq)  2 KNO3(aq) + PbI2(s)

24. No Precipitate Formation = No Reaction
KI(aq) + NaCl(aq)  KCl(aq) + NaI(aq)
All ions still present,  no reaction.

25. When an Aqueous Solution of Sodium Carbonate Is Added to an Aqueous Solution of Copper(II) Chloride, a White Solid Forms.
Write the formulas of the reactants and Determine the ions present when each reactant dissociates.
Na2CO3(aq) + CuCl2(aq) 
(Na+ + CO32-) + (Cu+2 + Cl-) 
Exchange the ions.
(Na+ + CO32-) + (Cu+2 + Cl-)  (Na+ + Cl-) + (Cu+2 + CO32-)

26. Write the formulas of the products.
Na2CO3(aq) + CuCl2(aq)  NaCl + CuCO3
Balance the equation.
Na2CO3(aq) + CuCl2(aq)  2 NaCl + CuCO3
Determine the solubility of each product. Write an (s) after the insoluble products and a (aq) after the soluble products
NaCl is soluble.
CuCO3 is insoluble.
Na2CO3(aq) + CuCl2(aq)  2 NaCl(aq) + CuCO3(s)

27. Practice–Predict the Products and Balance the Equation
KCl(aq) + AgNO3(aq) ®
Na2S(aq) + CaCl2(aq) ®

28. Practice–Predict the Products and Balance the Equation, Continued
KCl(aq) + AgNO3(aq) ®
KCl(aq) + AgNO3(aq) ® KNO3(aq) + AgCl(s)
Na2S(aq) + CaCl2(aq) ®
Na2S(aq) + CaCl2(aq) ® 2 NaCl(aq) + CaS(aq)
No reaction.

29. 2 KOH(aq) + Mg(NO3)2(aq) ® 2 KNO3(aq) + Mg(OH)2(s)
Ionic Equations
Equations that describe the chemicals put into the water and the product molecules are called molecular equations.
2 KOH(aq) + Mg(NO3)2(aq) ® 2 KNO3(aq) + Mg(OH)2(s)
Equations that describe the actual dissolved species are called complete ionic equations.
Aqueous electrolytes are written as ions.
Insoluble substances and nonelectrolytes written in molecule form.
2K+1(aq) + 2OH-1(aq) + Mg+2(aq) + 2NO3-1(aq) ® 2K+1(aq) + 2NO3-1(aq) + Mg(OH)2(s)

30. Ionic Equations An ionic equation in which the spectator ions are
Ions that are both reactants and products are called spectator ions.
2K+1(aq) + 2OH-1(aq) + Mg+2(aq) + 2NO3-1(aq) ® 2K+1(aq) + 2NO3-1(aq) + Mg(OH)2(s)
An ionic equation in which the spectator ions are
removed is called a net ionic equation.
2OH-1(aq) + Mg+2(aq) ® Mg(OH)2(s)

31. Summary
A molecular equation is a chemical equation showing the complete, neutral formulas for every compound in a reaction.
A complete ionic equation is a chemical equation showing all of the species as they are actually present in solution.
A net ionic equation is an equation showing only the species that actually participate in the reaction.