Chemistry - A Molecular Science

Chapter 11 Electron Transfer and Electrochemistry

cells convert chemical potential energy into electrical potential energy. If

Ecell

< 0, the

reaction is not spontaneous, and energy must

be supplied to the cell for the reaction to

occur. This type of cell is an electrolytic ce

ll. Electrolytic cells convert electrical potential

energy into chemical potential energy.

Metal corrosion is an electrochemical reaction that, in the case of iron, occurs on the

iron surface in the presence of water, oxygen, and some acid. The overall reaction is the oxidation of iron metal by atmospheric oxygen

to form iron(III) oxide. Galvanization and

passivation are two ways to protect metal surfaces from corrosion.

Batteries are galvanic cells. The lead-stora

ge battery in an automobile operates as a

galvanic cell when the car is started or when the lights are on but the engine is not. However, it operates as an electrolytic cell when the engine is running, and the battery is being recharged.

After studying the material in this chapter, you should be able to:

1. define oxidation and reduction and identify oxidizing and reducing agents (Section 11.1); 2. determine the number of electrons requir

ed to carry out an oxidation or a reduction

(Section 11.1);

3. identify an oxidizing agent and a reducing agent based on an orbital energy diagram

(Section 11.1);

4. write the half-reaction for a simple

oxidation or reduction (Section 11.2);

5. identify the anode and cathode, indicate t

he direction of electron flow, and explain the

function of the liquid junction in a galvanic cell (Section 11.3);

6. calculate standard cell potentials, give

n the standard reduction potentials of the half-

reactions (Section 11.4);

7. use a table of standard redu

ction potentials to write balanced redox reactions and to

predict if they would occur extensively (Section 11.5);

8. recognize common batteries and identify the anode and cathode (Section 11.6); 9. explain the corrosion of iron and how ga

lvanization and passivation can be used to

protect a metal from corroding (Section 11.7); and

10.

explain the workings of an electrolytic cell (Section 11.8).