Electrochemistry

Electrochemistry

• The flow of charged particles such as electrons in

a particular direction is called an electric current.

• Electrochemical cells that use spontaneous redox

reactions to create an electric current are called
voltaic cells.

SECTION1 Voltaic Cells: Electricity from Chemistry

Redox and Electrochemical Cells

Redox and Electrochemical Cells (cont.)

• The anode is the electrode at which the oxidation

reaction occurs.

• The cathode is the electrode at which the reduction

reaction occurs.

SECTION1

Voltaic Cells: Electricity from Chemistry

Multiple Choice

The _________is the electrode where oxidation occurs.

• anode

• cathode

• base

• electrolyte

Multiple Choice

The ________is the electrode where reduction occurs.

• anode

• cathode

• electrolyte

• acid

SECTION1 Voltaic Cells: Electricity from Chemistry

Redox and Electrochemical Cells (cont.)

• Electron potential is a

force, or a pressure of
electrons.

• The difference in electron pressure at the cathode and

at the anode is called potential difference.

• If there is no potential difference between the electrodes,

no current will flow.

SECTION1

Voltaic Cells: Electricity from Chemistry

Redox and Electrochemical Cells (cont.)

SECTION1

Voltaic Cells: Electricity from Chemistry

Redox and Electrochemical Cells (cont.)

• The size of the current depends on the size of the

potential difference.

• An electrical potential difference is called voltage.

• Different substances release different amounts of

energy when they become oxidized.

Multiple Choice

An electron potential difference is called

• voltage

• current

• resistance

• electricity

SECTION1

Voltaic Cells: Electricity from Chemistry

Redox and Electrochemical Cells (cont.)

SECTION1

Voltaic Cells: Electricity from Chemistry

Redox and Electrochemical Cells (cont.)

• In a voltaic cell, chemical energy is converted to

electrical energy.

• Voltaic cells are sometimes called galvanic cells.

• In order for electric current to flow, a wire connecting

the electrodes and a salt bridge must be present to
complete the circuit.

Multiple Choice

A voltaic cell is sometimes called a

• galvanic cell

• battery cell

• endoplasmic cell

• polar cell

SECTION1

Voltaic Cells: Electricity from Chemistry

Redox and Electrochemical Cells (cont.)

• A salt bridge allows

the passage of ions
from one side to
another so that an
excess charge
does not build up
around the
electrodes.

SECTION1

Voltaic Cells: Electricity from Chemistry

Redox and Electrochemical Cells (cont.)

• Positive ions are called cations.

• Negative ions are called anions.

Match

Match the following

• Positive ions

• Negative ions

• Passage for ions

cations

anions

salt bridge

• cations

• anions

• salt bridge

SECTION1

Voltaic Cells: Electricity from Chemistry

Redox and Electrochemical Cells (cont.)

• Without an external circuit, a voltaic cell cannot be

created.

• The amount of energy released depends on two

properties of the cell: the amount of material that
is present and the potential difference between
the electrodes.

SECTION1

Voltaic Cells: Electricity from Chemistry

Redox and Electrochemical Cells (cont.)

• The farther apart two substances are on the ease of

oxidation table, the greater the potential difference
between the electrodes, and the greater the energy
delivered by each electron that flows through the
external wire.

SECTION1

Voltaic Cells: Electricity from Chemistry

Batteries

• A battery is one

or more voltaic
cells in a single
package that
generates electric
current.

SECTION1

Voltaic Cells: Electricity from Chemistry

Batteries (cont.)

• The total voltage is the sum of the voltages of the

individual cells.

SECTION1

Voltaic Cells: Electricity from Chemistry

Carbon-Zinc Dry Cell

• Carbon-zinc voltaic cells

are often called dry cells
because a semi-solid
paste is used instead of
an aqueous electrolyte
solution.

SECTION1

Voltaic Cells: Electricity from Chemistry

Carbon-Zinc Dry Cell (cont.)

• The circuit is designed to be complete once the voltaic

cells are placed in something designed to be powered
by it, such as a flashlight.

SECTION1

Voltaic Cells: Electricity from Chemistry

Automobile Lead Storage Battery

• The most common type of battery used in cars is a

lead-acid, 12-volt storage battery.

– more durable

– supplies a large current

– can be recharged

SECTION1

Voltaic Cells: Electricity from Chemistry

Automobile Lead Storage Battery (cont.)

• The electrolyte solution is sulfuric acid.

• In each cell, lead metal is oxidized as lead (IV) oxide

is reduced.

• The reaction that discharges a lead-acid battery is

spontaneous and requires no energy.

Multiple Choice

A car battery use ______________ as an electrolyte.

• an alkaline paste

• sulfuric acid

• a salt bridge

SECTION1

Voltaic Cells: Electricity from Chemistry

Automobile Lead Storage Battery (cont.)

• The reverse reaction, which recharges the battery, is

not spontaneous and requires an input of electricity
from the car’s alternator.

Multiple Choice

A (n) _______________is used to recharge a car battery.

• alternator

• radio

• solar cell

• transmission

SECTION1

Voltaic Cells: Electricity from Chemistry

Electric Cars (cont.)

• Disadvantages of electric cars

– high initial cost

– limited driving range

– low speed

– long recharge time

– issues with disposal

SECTION2

Electrolysis: Chemistry from Electricity

electrolysis

electrolytic cell

In electrolysis, a power source causes
nonspontaneous reactions to occur in
electrochemical cells.

New Vocabulary

• At the cathode, the ion that reacts is the one that most

readily accepts electrons.

• At the anode, electrons are transferred from the ion that

most easily gives them up to the anode.

SECTION2

Electrolysis (Cont.)

Electrolysis: Chemistry from Electricity

CHAPTER
17

Standardized Test Practice

Electrochemistry

Which yields a higher voltage—a copper penny
with an iron nail in it or a copper penny with a
piece of nickel in it?

A. They yield the same voltage.

B. copper penny with a piece of nickel

C. copper penny with an iron nail