1. Chapter 8 Chemical Reaction
Section 1 Describing Chemical Reactions
Chapter 8
Chemical Reaction
A chemical reaction is the process by which one or more substances change into one or more new substances.
Reactants are the original substances in a chemical reaction.
Products are the substances that are created in a chemical reaction.

2. Chapter 8
Visual Concepts
Chemical Reaction

3. Evidence of a Chemical Reaction
Section 1 Describing Chemical Reactions
Chapter 8
Evidence of a Chemical Reaction

4. Signs of a Chemical Reaction
Chapter 8
Visual Concepts
Signs of a Chemical Reaction

5. Chapter 8
Visual Concepts
Precipitate

6. Evidence of a Chemical Reaction
Section 1 Describing Chemical Reactions
Chapter 8
Evidence of a Chemical Reaction
solution color changes
solution bubbles
copper is used up

7. Chemical Reaction Versus Physical Change
Section 1 Describing Chemical Reactions
Chapter 8
Chemical Reaction Versus Physical Change
chemical change – new substance forms with properties that differ from original substance
density
boiling point
melting point
physical change - changes of state
evaporation
condensation
melting
freezing

8. Reactions and Energy Changes
Section 1 Describing Chemical Reactions
Chapter 8
Reactions and Energy Changes
Energy can be released in a chemical reaction.
methane + oxygen  carbon dioxide + water + energy
Energy is a product.
Energy can be absorbed in a chemical reaction.
dinitrogen tetroxide + energy  nitrogen dioxide
Energy is a reactant.

9. Constructing a Chemical Equation
Section 1 Describing Chemical Reactions
Chapter 8
Constructing a Chemical Equation
A chemical equation shows the chemical formulas and relative amounts of all reactants and products.
A word equation contains the names of the reactants and products.
Equations must be balanced.

10. methane + oxygen  carbon dioxide + water
Section 1 Describing Chemical Reactions
Chapter 8
Writing a Word Equation or Formula Equation
methane + oxygen  carbon dioxide + water
?CH ?O2  ?CO ?H2O

11. Equations and Reaction Information
Section 1 Describing Chemical Reactions
Chapter 8
Equations and Reaction Information
Physical States
NaHCO3(s) + HC2H3O2(aq)  NaC2H3O2(aq) + CO2(aq) + H2O(l)
solid liquid
aqueous solutions
Reaction Conditions
350°C, kPa
N2(g) + 3H2(g)
2NH3(g)
catalyst

12. Equations and Reaction Information
Section 1 Describing Chemical Reactions
Chapter 8
Equations and Reaction Information

13. Chapter 8
Visual Concepts
Chemical Equation

14. Reactions Conserve Mass
Section 2 Balancing Chemical Equations
Chapter 8
Reactions Conserve Mass
Mass cannot be created or destroyed by a chemical or physical change
Equations must be balanced.
?Na + ?H2O  ?NaOH + ?H2

15. Chapter 8 Balancing Equations
Section 2 Balancing Chemical Equations
Chapter 8
Balancing Equations
The number of atoms for each element must be the same on the reactants’ side and on the products’ side.
A coefficient multiplies the number of atoms of each element in the formula that follows.
H2O: 2 hydrogen atoms, 1 oxygen atom
2H2O: 4 hydrogen atoms, 2 oxygen atoms

16. Reading a Chemical Equation
Chapter 8
Visual Concepts
Reading a Chemical Equation

17. Balancing a Chemical Equation by Inspection
Chapter 8
Visual Concepts
Balancing a Chemical Equation by Inspection

18. Chapter 8 Balancing Equations Sample Problem A
Section 2 Balancing Chemical Equations
Chapter 8
Balancing Equations
Sample Problem A
Balance the equation for the reaction of iron(III) oxide with hydrogen to form iron and water.

19. Chapter 8 Balancing Equations Sample Problem A Solution
Section 2 Balancing Chemical Equations
Chapter 8
Balancing Equations
Sample Problem A Solution
Identify reactants and products.
reactants products
Fe2O H2  Fe + H2O
Count atoms 3 2 3
Reactants
Products
Balanced?
Unbalanced formula equation
Fe2O3 + H2
Fe + H2O
Iron atoms 2 1 no
Oxygen atoms 3
Hydrogen atoms
yes
Insert coefficients.

20. Reactions Conserve Mass
Section 2 Balancing Chemical Equations
Chapter 8
Reactions Conserve Mass
Balanced equations show mass conservation
?Na + ?H2O  ?NaOH + ?H2
2Na + 2H2O  2NaOH + H2
Never change subscripts to balance equations
Unbalanced: H2 + O2  H2O
Incorrect: H2 + O2  H2O2
H2O  H2O2
Correct: 2H2 + O2  2H2O

21. Reactions Conserve Mass
Section 2 Balancing Chemical Equations
Chapter 8
Reactions Conserve Mass

22. Polyatomic Ions can be balanced as a group
Section 2 Balancing Chemical Equations
Chapter 8
Polyatomic Ions can be balanced as a group

23. Chapter 8 Balancing Equations
Section 2 Balancing Chemical Equations
Chapter 8
Balancing Equations
Sample Problem C
Aluminum reacts with arsenic acid, HAsO3, to form H2 and aluminum arsenate. Write a balanced equation for this reaction.

24. Chapter 8 Balancing Equations reactants products 2 6 3 2
Section 2 Balancing Chemical Equations
Chapter 8
Balancing Equations
Sample Problem C Solution
1. Identify reactants and products.
reactants products
Al + HAsO3  H Al(AsO3)3
2. Count Atoms 2 6 3 2
Reactants
Products
Balanced?
Unbalanced formula equation
Al + HAsO3
H2 + Al(AsO3)3
Iron atoms 1
yes
Oxygen atoms 2 no
Hydrogen atoms 3
3. Insert coefficients

25. Chapter 8 Combustion Reactions
Section 3 Classifying Chemical Reactions
Chapter 8
Combustion Reactions
A combustion reaction is a reaction of a carbon-based compound with oxygen.
Combustion of propane:
C3H8 + 5O2  3CO2 + 4H2O
Combustion of ethanol:
CH3CH2OH + 3O2  2CO2 + 3H2O

26. Chapter 8
Visual Concepts
Combustion Reaction

27. CaO(s) + H2O(l)  Ca(OH)2(s)
Section 3 Classifying Chemical Reactions
Chapter 8
Synthesis Reactions
In a synthesis reaction a single compound forms from two or more reactants.
Two elements form a binary compound
C + O2  CO2
2C + O2 2CO
Two compounds form a ternary compound
CaO(s) + H2O(l)  Ca(OH)2(s)
CO2(g) + H2O(l)  H2CO3(aq)

28. Chapter 8
Visual Concepts
Synthesis Reactions

29. Decomposition Reactions
Section 3 Classifying Chemical Reactions
Chapter 8
Decomposition Reactions
In a decomposition reaction a single compound breaks down, often with the input of energy, into two or more elements or simpler compounds.
Decomposition of water
electricity
2H2O(l)
O2(g) + 2H2(g)
A metal carbonate decomposes to form a metal oxide and carbon dioxide.
heat
CaCO3(s)
CaO(s) + CO2(g)

30. Decomposition Reaction
Chapter 8
Visual Concepts
Decomposition Reaction

31. Chapter 8
Visual Concepts
Electrolysis

32. Decomposition Reactions, continued
Section 3 Classifying Chemical Reactions
Chapter 8
Decomposition Reactions, continued
Sample Problem D
Predicting Products
Predict the product(s) and write a balanced equation for the reaction of potassium with chlorine.

33. Decomposition Reactions, continued
Section 3 Classifying Chemical Reactions
Chapter 8
Decomposition Reactions, continued
Sample Problem D Solution
Reaction is most likely a synthesis reaction, so the product will be binary
Potassium will lose one electron to become a 1+ ion.
Chlorine will gain one electron to become a 1– ion.
K + Cl2  KCl
Balance the equation.
2K + Cl2  2KCl

34. Displacement Reactions
Section 3 Classifying Chemical Reactions
Chapter 8
Displacement Reactions
In a displacement reaction a single element reacts with a compound and displaces another element from the compound.
2Al(s) + 3CuCl2(aq)  2AlCl3(aq) + 3Cu(s)
Aluminum displaces copper.

35. Single Displacement Reaction
Chapter 8
Visual Concepts
Single Displacement Reaction

36. Displacement Reactions, continued
Section 3 Classifying Chemical Reactions
Chapter 8
Displacement Reactions, continued
The activity series ranks the reactivity of elements

37. Chapter 8
Visual Concepts
Activity Series

38. Displacement Reactions, continued
Section 3 Classifying Chemical Reactions
Chapter 8
Displacement Reactions, continued
Sample Problem E
Determining Products by Using the Activity Series Magnesium is added to a solution of lead(II) nitrate. Will a reaction happen? If so, write the equation and balance it.

39. Displacement Reactions, continued
Section 3 Classifying Chemical Reactions
Chapter 8
Displacement Reactions, continued
Sample Problem E Solution
Identify the reactants.
Magnesium will attempt to displace lead from lead(II) nitrate.
Check the activity series.
Magnesium is more active than lead and displaces it.
Write the balanced equation.
Mg + Pb(NO3)2  Pb + Mg(NO3)2

40. HCl(aq) + NaOH(aq)  HOH(l) + NaCl(aq)
Section 3 Classifying Chemical Reactions
Chapter 8
Double-Displacement Reactions
In a double-displacement reaction two compounds in aqueous solution appear to exchange ions and form two new compounds.
One of the products must be a solid precipitate, a gas, or a molecular compound, such as water.
HCl(aq) + NaOH(aq)  HOH(l) + NaCl(aq)

41. Double-Displacement Reaction
Chapter 8
Visual Concepts
Double-Displacement Reaction

42. Precipitation Reaction
Chapter 8
Visual Concepts
Precipitation Reaction

43. Chapter 8
Identifying Reactions and Predicting Products

44. Ionic Equations, continued
Section 4 Writing Net Ionic Equations
Chapter 8
Ionic Equations, continued
Ionic compounds dissolve in water
KI(aq) = K+(aq) + I–(aq)
Pb(NO3)2(aq) = Pb2+(aq) (aq)
Reaction between KI and Pb(NO3)2
2KI(aq) + Pb(NO3)2(aq)  PbI2(s) + 2KNO3(aq)
Total Ionic Equation
2K+(aq) + 2I–(aq) + Pb2+(aq) (aq)
 PbI2(s) + 2K+(aq) (aq)

45. 2I–(aq) + Pb2+(aq)  PbI2(s)
Section 4 Writing Net Ionic Equations
Chapter 8
Ionic Equations, continued
Spectator ions remain unchanged in the solution as aqueous ions. They do not react.
2K+(aq) + 2I–(aq) + Pb2+(aq) (aq)
 PbI2(s) + 2K+(aq) (aq)
The net ionic equation is the chemical equation that shows only the net change.
2I–(aq) + Pb2+(aq)  PbI2(s)

46. Chapter 8
Visual Concepts
Net Ionic Equation

47. Zn(s) + Cu2+(aq)  Cu(s) + Zn2+(aq)
Section 4 Writing Net Ionic Equations
Chapter 8
Ionic Equations, continued
Net Ionic equations can be used for displacement reactions.
Zn(s) + Cu2+(aq) (aq)  Cu(s) + Zn2+(aq) (aq)
net ionic equation
Zn(s) + Cu2+(aq)  Cu(s) + Zn2+(aq)

48. Ionic Equations, continued
Section 4 Writing Net Ionic Equations
Chapter 8
Ionic Equations, continued
Check atoms and charge to balance net ionic equations.
(aq) + Ba2+(aq)  BaSO4(s)
Charge: (2–) + (2+) =
Zn(s) + Cu2+(aq)  Cu(s) + Zn2+(aq)
Charge:

49. Chapter 8
Writing a Net Ionic Equation

50. Understanding Concepts
Chapter 8
Standardized Test Preparation
Understanding Concepts
1. What type of chemical reaction involves the exchange of the ions of two compounds in an aqueous solution to form two new compounds?
A. synthesis reaction
B. decomposition reaction
C. single-displacement reaction
D. double-displacement reaction

51. Understanding Concepts
Chapter 8
Standardized Test Preparation
Understanding Concepts
1. What type of chemical reaction involves the exchange of the ions of two compounds in an aqueous solution to form two new compounds?
A. synthesis reaction
B. decomposition reaction
C. single-displacement reaction
D. double-displacement reaction

52. Understanding Concepts
Chapter 8
Standardized Test Preparation
Understanding Concepts
2. Which of these sentences correctly states the law of conservation of mass?
F. In a chemical reaction, the mass of the products cannot exceed the mass of the reactants.
G. In a chemical reaction, the mass of the products is always equal to the mass of the reactants.
H. In a chemical reaction, the mass of the products is always less than the mass of the reactants.
I. In a chemical reaction, the mass of the products is always greater than the mass of the reactants.

53. Understanding Concepts
Chapter 8
Standardized Test Preparation
Understanding Concepts
2. Which of these sentences correctly states the law of conservation of mass?
F. In a chemical reaction, the mass of the products cannot exceed the mass of the reactants.
G. In a chemical reaction, the mass of the products is always equal to the mass of the reactants.
H. In a chemical reaction, the mass of the products is always less than the mass of the reactants.
I. In a chemical reaction, the mass of the products is always greater than the mass of the reactants.

54. Understanding Concepts
Chapter 8
Standardized Test Preparation
Understanding Concepts
3. Of these reaction types, which has only one reactant?
A. decomposition
B. displacement
C. oxidation
D. synthesis

55. Understanding Concepts
Chapter 8
Standardized Test Preparation
Understanding Concepts
3. Of these reaction types, which has only one reactant?
A. decomposition
B. displacement
C. oxidation
D. synthesis

56. Understanding Concepts
Chapter 8
Standardized Test Preparation
Understanding Concepts
4. Write a net ionic equation, excluding spectator ions, for the reaction:
Mg(s) + Zn(NO3)2(aq)  Zn(s) + Mg(NO3)2(aq)

57. Understanding Concepts
Chapter 8
Standardized Test Preparation
Understanding Concepts
4. Write a net ionic equation, excluding spectator ions, for the reaction:
Mg(s) + Zn(NO3)2(aq)  Zn(s) + Mg(NO3)2(aq)
Answer: Mg(s) + Zn2+(aq)  Mg2+(aq) + Zn(s)

58. Understanding Concepts
Chapter 8
Standardized Test Preparation
Understanding Concepts
5. Differentiate between formula equations and balanced chemical equations.

59. Understanding Concepts
Chapter 8
Standardized Test Preparation
Understanding Concepts
5. Differentiate between formula equations and balanced chemical equations.
Answer: Formula equations give the identity of the reactants and the products, but a balanced equation shows equal numbers of atoms of each element on both sides.

60. Understanding Concepts
Chapter 8
Standardized Test Preparation
Understanding Concepts
6. Write a balanced equation for this reaction:
iron(III) nitrate + lithium hydroxide 
lithium nitrate + iron(III) hydroxide

61. Understanding Concepts
Chapter 8
Standardized Test Preparation
Understanding Concepts
6. Write a balanced equation for this reaction:
iron(III) nitrate + lithium hydroxide 
lithium nitrate + iron(III) hydroxide
Answer: Fe(NO3)3 + 3LiOH  3LiNO3 + Fe(OH)3

62. Chapter 8 Reading Skills
Standardized Test Preparation
Reading Skills
Read the passage below. Then answer the questions.
A student places a strip of pure magnesium metal into a test tube containing a dilute solution of hydrochloric acid (hydrogen chloride dissolved in water). As the magnesium disappears, bubbles of a colorless gas form and the test tube becomes hot to the touch. If a lit match is placed near the top of the test tube, the gas that has been generated burns.

63. Chapter 8 Reading Skills
Standardized Test Preparation
Reading Skills
7. What evidence is there that a chemical reaction has occurred?

64. Chapter 8 Reading Skills
Standardized Test Preparation
Reading Skills
7. What evidence is there that a chemical reaction has occurred?
Answer: The gas that burns is a different chemical substance than any of the reactants, indicating a chemical reaction.

65. Chapter 8 Reading Skills
Standardized Test Preparation
Reading Skills
8. Based on the substances present in the reaction, what is the most likely identity of the reaction product that burns in air?
F. hydrogen
G. magnesium
H. oxygen
I. oxygen and hydrogen mixture

66. Chapter 8 Reading Skills
Standardized Test Preparation
Reading Skills
8. Based on the substances present in the reaction, what is the most likely identity of the reaction product that burns in air?
F. hydrogen
G. magnesium
H. oxygen
I. oxygen and hydrogen mixture

67. Chapter 8 Reading Skills
Standardized Test Preparation
Reading Skills
9. Which of these equations is a balanced chemical equation for the reaction described above?
A. Mg(s) + HCl(aq)  MgCl2(aq) + H2(g) + energy
B. Mg(s) + 2HCl(aq) + energy  MgCl2(aq) + H2(g)
C. Mg(s) + 2HCl(aq)  MgCl2(aq) + H2(g) + energy
D. 2Mg(s) + 2HCl(aq)  2MgCl2(aq) + H2(g) + energy

68. Chapter 8 Reading Skills
Standardized Test Preparation
Reading Skills
9. Which of these equations is a balanced chemical equation for the reaction described above?
A. Mg(s) + HCl(aq)  MgCl2(aq) + H2(g) + energy
B. Mg(s) + 2HCl(aq) + energy  MgCl2(aq) + H2(g)
C. Mg(s) + 2HCl(aq)  MgCl2(aq) + H2(g) + energy
D. 2Mg(s) + 2HCl(aq)  2MgCl2(aq) + H2(g) + energy

69. Interpreting Graphics
Chapter 8
Standardized Test Preparation
Interpreting Graphics
The table below shows the reactivity of selected
elements. Use it to answer questions 10 through 12.

70. Interpreting Graphics
Chapter 8
Standardized Test Preparation
Interpreting Graphics
10.Which of these elements will produce a flammable product when placed in water at room temperature?
F. aluminum
G. silver
H. sodium
I. zinc

71. Interpreting Graphics
Chapter 8
Standardized Test Preparation
Interpreting Graphics
10.Which of these elements will produce a flammable product when placed in water at room temperature?
F. aluminum
G. silver
H. sodium
I. zinc

72. Interpreting Graphics
Chapter 8
Standardized Test Preparation
Interpreting Graphics
11.Which of these combinations is most likely to cause a displacement reaction?
A. a zinc strip placed in a solution of aluminum
chloride
B. a nickel strip placed in a solution of calcium chloride
C. a silver strip placed in a solution of potassium
hydroxide
D. an aluminum strip placed in a solution of copper

73. Interpreting Graphics
Chapter 8
Standardized Test Preparation
Interpreting Graphics
11.Which of these combinations is most likely to cause a displacement reaction?
A. a zinc strip placed in a solution of aluminum
chloride
B. a nickel strip placed in a solution of calcium chloride
C. a silver strip placed in a solution of potassium
hydroxide
D. an aluminum strip placed in a solution of copper

74. Interpreting Graphics
Chapter 8
Standardized Test Preparation
Interpreting Graphics
12.What determines the order of the elements in the activity series?
F. increasing atomic number
G. increasing electronegativity
H. increasing ionization energy
I. experimentally determined reactivity

75. Interpreting Graphics
Chapter 8
Standardized Test Preparation
Interpreting Graphics
12.What determines the order of the elements in the activity series?
F. increasing atomic number
G. increasing electronegativity
H. increasing ionization energy
I. experimentally determined reactivity