Review Chapter 6:
Oxidation & Reduction
Reactions
Chemistry: The Molecular Nature of Matter,
6th edition
By Jesperson, Brady, & Hyslop
Chapter 6 Concepts
 Be very familiar with the difference between oxidation and reduction
 Identify a redox reaction (look for changing oxidation numbers)
 Determine oxidation numbers and identify oxidizing and reducing
agents
 Balance redox reactions either using
 The half reaction method (ion-electron method)
 The atom conservation method
 Predict the products of:
 Combustion reactions
 Single replacement reactions
 acids as oxidizing agents
 Recognize combustion, corrosion, and single replacement
reactions
2
Define Oxidation & Reduction
Oxidation = loss of electrons
Reduction = gain electrons
An oxidizing agent is reduced as it oxidizes another compound
A reducing agent is oxidized as it reduces another compound
A redox reaction always has one one element being oxidized and
another being reduced, identifying these confirms the reaction is a
redox reaction.
Memorize: Rules for Assigning Ox #
1.
2.
3.
4.
5.
6.
7.
8.
9.
Assigning Oxidation Numbers
Oxidation numbers must add up to charge on molecule, formula unit or
ion.
Atoms of free elements have oxidation numbers of zero.
Metals in Groups 1A, 2A, and Al have +1, +2, and +3 oxidation
numbers, respectively.
H and F in compounds have +1 and –1 oxidation numbers, respectively.
Oxygen has –2 oxidation number.
Group 7A elements have –1 oxidation number.
Group 6A elements have –2 oxidation number.
Group 5A elements have –3 oxidation number.
When there is a conflict between two of these rules or ambiguity in
assigning an oxidation number, apply rule with lower oxidation number
and the rule higher on this priority list, and ignore conflicting rule
Memorize: Balanced Redox Reactions
The Half-Reaction Method:
1. Divide equation into two half-reactions
2. Balance atoms other than H and O
3. Balance O by adding H2O to side that needs O
4. Balance H by adding H+ to side that needs H
5. Balance net charge by adding e–
6. Make electron gain equal electron loss; then add half-reactions
7. Cancel electrons and anything that is the same on both sides
If balancing in basic conditions:
8. Add the same number of OH– to both sides of the equation as
there are H+
9. Combine H+ and OH– to form H2O
10. Cancel any H2O that you can from both sides
Memorize: Balanced Redox Reactions
The Atom-Conservation Method:
1. Identify the side of the reaction with greater negative charge (ie, more anions) and add H+.
2. On the opposite side of the reaction from where the H+ was added include H2O to balance
out the new hydrogen atoms.
3. Assign variables to the coefficients in front of every molecule or compound.
4. Set up equations for each element in the reaction setting the sum of the atoms on the
reactant side of the equation equal to the sum of the atoms on the product side of the
equation. Include an equation describing the charge balance of the reaction.
5. Chose a variable and assume it is equal to 1.
6. Solve the remaining equations.
7. Multiply all of the coefficients by the same number to ensure they are all whole numbers.
If balancing in basic conditions:
8. Add the same number of OH– to both sides of the equation as there are H+
9. Combine H+ and OH– to form H2O
10. Cancel any H2O that you can from both sides
Types of Redox Reactions
Combustion
Excess oxygen: CxHy + O2  CO2 + H2O
Excess oxygen: CxHySz + O2  CO2 + H2O + SO2
Limited oxygen: CxHy + O2  CO + H2O
Very Limited oxygen: CxHy + O2  C + H2O
Corrosion
Metal: M (s) + O2 (g)  MxOy
Nonmetal: S (s) + O2 (g)  SO2
N (g) + O2 (g)  NO or NO2 or N2O or N2O3 or N2O4 or N2O5
Single Replacement
M (s) + NxBy (aq)  MwBz (aq) + N (s)
• where M and N are either metals or nonmetals
Acids as Oxidizing Agents
Acids:
HA = H+ + AH+ is a stronger
oxidizing agent then A-
A- is a stronger
oxidizing agent then H+
Non-Oxidizing
Acids
Oxidizing
Acids
A- 
H+  H2 (g)
H+ is the oxidizing agent
H2 is the reduction product
Examples:
HCl, HBr, HI
Organic Acids (CH3CO2H)
H3PO4
H2SO4 if cold & dilute
A- reduction product
H2SO4
With Strong Reducing
Agent:
H2SO4  H2S (g)
With a Moderate or Weak
Reducing Agent:
H2SO4  SO2 (g)
HNO3
Concentrated:
NO3–  NO2 (g)
Dilute:
NO3–  NO (g)
Be Familiar with Activity Series
M (s) + NxBy (aq)  MwBz (aq) + N (s)
If M and N are both metals then
M = element and N = Oxidizing Agent
Element
Oxidizing
Agent
Rxn
Will
Occur
Rxn
Won’t
Occur