1. Chapter 5 Chemical Reactions
Chemistry 140
Chapter 5
Chemical Reactions

2. CHAPTER OUTLINE 5.1 Chemical Equations 5.2 Types of Reactions
5.3 Redox Reactions
5.4 Decomposition Reactions
5.5 Combination Reactions
5.6 Replacement Reactions
5.7 Ionic Equations
5.8 Energy and Reactions
5.9 The Mole and Chemical Equations
5.10 The Limiting Reactant
5.11 Reaction Yields

3. LEARNING OBJECTIVES/ASSESSMENT
When you have completed your study of this chapter, you should be able to:
1. Identify the reactants and products in written reaction equations, and balance the equations by inspection. (Section 5.1; Exercises 5.2 and 5.6)
2. Assign oxidation numbers to elements in chemical formulas, and identify the oxidizing and reducing agents in redox reactions. (Section 5.3; Exercises 5.10 and 5.15)
3. Classify reactions into the categories of redox or nonredox, then into the categories of decomposition, combination, single replacement, or double replacement. (Sections 5.4, 5.5, and 5.6; Exercise 5.20)
4. Write molecular equations in total ionic and net ionic forms. (Section 5.7; Exercise 5.30 a, b, & c)
5. Classify reactions as exothermic or endothermic. (Section 5.8; Exercise 5.34)
6. Use the mole concept to do calculations based on chemical reaction equations. (Section 5.9; Exercise 5.42)
7. Use the mole concept to do calculations based on the limiting‐reactant principle. (Section 5.10; Exercise 5.52)
8. Use the mole concept to do percentage‐yield calculations. (Section 5.11; Exercise 5.56)

4. Describing Chemical Reactions
chemical reaction - a change in matter in which a substance with new identities is formed
Indications of a chemical reaction
production of heat
production of light
change in color
production of a gas

5. Facts about chemical reactions.
Chemical reactions release or absorb energy.
release energy - exothermic
absorb energy - endothermic
Atoms are rearranged in a chemical change.
atoms cannot be created or destroyed
coefficients are adjusted to satisfy the law of conservation of matter
Particles must collide for a chemical reaction to occur.
reactant particles must come in contact with each other

6. How are reactions written?
1. Equations represent facts - write a word equation.
2. Substitute symbols and formulas for elements and compounds.
3. Use charges of ions to write formulas for compounds.
4. Balance the equation by adjusting coefficients.

7. Sample Equation 1
1. hydrogen + oxygen water
2. H2 + O2  H2O
3. formulas are correct
4. 2H2 + O2  2H2O

8. Sample Equation 2
1. calcium carbonate  calcium oxide + carbon dioxide 2. 3. 4

9. Practice Problems 1. zinc + sulfur  zinc sulfide Zn + S  ZnS
2. sodium chloride + silver nitrate  silver chloride + sodium nitrate
NaCl +AgNO3  AgCl + NaNO3
3. potassium + water  potassium hydroxide + hydrogen
2K + 2H2O  2KOH + H2
4. sodium hydroxide + hydrochloric acid (HCl)  sodium chloride + water
NaOH + HCl  NaCl + HOH

10. More Practice Problems
5. magnesium bromide + chlorine  magnesium chloride + bromine
MgBr2 + Cl2  MgCl2 + Br2
6. sodium chloride + sulfuric acid (H2SO4)  sodium sulfate + hydrogen chloride
7. aluminum + iron(III) oxide  aluminum oxide + iron
8. butane + oxygen  carbon dioxide + water

11. What information is in an equation?
qualitative - tells what is present
names, formulas, etc.
(s) solid, (l) liquid, (g) gas
(aq) aqueous - in water solution
quantitative - tells how much is present
coefficients represent quantity of moles
energy may be given
left side - endothermic
right side - exothermic

12. Describe the following equation in words.
C6H12O6(aq) + 6O2(g) 6CO2(g) + 6H2O(l) kJ
One mole of aqueous glucose reacts with 6 moles of oxygen gas to produce 6 moles of carbon dioxide gas, 6 moles of water and 2870kJ of energy is given for each mole of glucose reacting.

13. Types of Chemical Reactions
Combustion - oxygen combines with hydrocarbons
C2H6(g) + O2(g) CO2(g) + H2O(l)
Any substance that burns in air reacts with oxygen.

14. Synthesis
Synthesis - two or more substances combine to form more complex substances.
A + B  AB
Example: P4(s) + 6Cl2(g)  4PCl3(l)

15. Decomposition Reactions
Decomposition - complex substances are broken down into simpler substances.
AB  A + B
Example: 2HgO  2Hg + O2

16. Single Replacement Reactions
Single Replacement - a substance in one compound is replaced by another substance.
A + BC  AC + B
Example:
Mg(s) + 2HCl(aq)  MgCl2(s) + H2(g)

17. Double Replacement Reactions
Double Replacement - two substances exchange components.
AB + CD  AD + CB
Example:
NaCl + AgNO3  AgCl + NaNO3

18. Predicting Products of Decomposition Reactions
1. Decomposition of a metallic carbonate yields a metallic oxide and carbon dioxide.
2. Decompostion of a metallic chlorate yields a metallic chloride and oxygen.
3. Decomposition of a metallic hydroxide yields a metallic oxide and water.
4. Decomposition of a metallic nitrate yields a metallic nitrite and oxygen.