1. Chapter 5 Chemical Quantities and Reactions
5.5
Oxidation−Reduction Reactions

2. Oxidation−Reduction Reactions
An oxidation–reduction reaction
provides us with energy from food
provides electrical energy in batteries
occurs when iron rusts:
4Fe(s) + 3O2(g) Fe2O3(s)

3. Oxidation−Reduction In an oxidation–reduction reaction, electrons are
transferred from one substance to another.

4. Oxidation−Reduction
Reduced Oxidized

5. Oxidation and Reduction
2Cu(s) + O2(g) CuO
OIL RIG
Oxidation is loss of electrons.
2Cu(s) Cu2+(s) + 4e−
Reduction is gain of electrons.
O2(g) + 4e− O2− (s)
The green patina on copper is due to oxidation

6. Zn replaces Cu2+

7. Zn Transfers Electrons to Cu2+
OIL Oxidation is losing electrons.
RIG Reduction is gaining electrons.

8. Learning Check
Identify each of the following as oxidation or reduction:
__A. Sn(s) Sn4+(aq) + 4e−
__B. Fe3+(aq) + 1e− Fe2+(aq)
__C. Cl2(g) + 2e− Cl− (aq)

9. Solution Identify each of the following as oxidation or reduction:
Oxidation __A. Sn(s) Sn4+(aq) + 4e−
Reduction __B. Fe3+(aq) + 1e− Fe2+(aq)
Reduction __C. Cl2(g) + 2e− Cl− (aq)

10. Learning Check In light-sensitive sunglasses, UV light initiates an
oxidation–reduction reaction.
UV light
2Ag Cl− Ag + Cl2
A. Which reactant is oxidized?
B. Which reactant is reduced?

11. Solution In light-sensitive sunglasses, UV light initiates an
oxidation-reduction reaction.
uv light
2Ag Cl− Ag + Cl2
A. Which reactant is oxidized? 2Cl− Cl e−
B. Which reactant is reduced? 2Ag e− Ag

12. Oxidation–Reduction in Biological Systems
The oxidation of a typical biochemical molecule can
involve the transfer of two hydrogen atoms (or 2H+ and
2e−) to a proton acceptor such as the coenzyme FAD (flavin
adenine dinucleotide).

13. Characteristics of Oxidation and Reduction

14. Characteristics of Oxidation and Reduction
Methyl alcohol formaldehyde Oxidation (loss of H as
hydrogen gas)
CH3OH H2CO + 2H2
Formaldehyde formic acid
2H2CO + O H2CO Oxidation (addition of O)