CHAPTER 6 ELECTROCHEMISTRY
Electrolyte
6.1 ELECTROLYTIC CELL
is a study in chemistry of the relationship
between electrical and chemical
A.
Electrolytic
cell
Electric current flows through
an electrolyte to produce
a chemical reaction.
Change of energy :
Electrical energy
Chemical energy
Name of
process
B.
Chemical
cell
Electrolysis
Chemical changes that occur
in the cell produce an electric
current.
Chemical energy
electrical energy
ELECTROLYSIS
Decomposition of a compound in the
molten or aqueous state into its
constituent
elements when electric current flows
through it. What are the decomposed
Source of
electric
Electrode
Battery
-To produce electric current
to carry out electrolysis
Rod that can conduct
electricity
Anode The electrode
connected to
the positive
terminal.
Catho the electrode
de
connected to the
negative terminal.
Substances in the m
Electrolytes are ionic
compounds in the molten or
aqueous state which consist
of positive ions, (cations) and
negative ions, (anions.)
*molten-contain 2 ions
* aqueous-contains 3 / 4 ions
Anions Negative ions
(-)
Cation Positive ions
s
(+)
During the electrolysis process:
 Cations move to Cathode
 Anions move to Anode
atoms of the metal
which
are then deposited
at the cathode
an electrolytic cell half-filled with 0.1 mol
dm–3
copper(II) sulphate solution, CuSO4 , and
two test tubes filled completely with 0.1
mol dm–3 copper(II) sulphate solution,
CuSO4
FACTORS AFFECTING THE PRODUCTS OF
ELECTROLYSIS
1.position
Ions at the bottom of the
of ions in
electrochemical series have
the
higher tendencies to be
electroche discharged.
mical series
2.
concentrati
on of
electrolyte
3. types of
electrode
Negative ions which are more
concentrated in an
electrolyte are more likely to
be discharged
at the anode.
If the metal used as the
anode is the same as the
metal ion in the electrolyte,
Anode Thinning
:
the metal atoms will
ionise to form
positive ions that
dissolve into
electrolyte
Catho Thicker
de
the metal ions will
discharge to form
APPLICATION OF ELECTROLYSIS IN
INDUSTRIES
1.Extractio To extract metals from their
n of metals molten ores or salts (that are
more reactive than
*factor
carbon,)eg: potassium,
used:
sodium ,calcium, magnesium
concentrati & aluminium
on of
electrolyte Electrode: carbon
Electrolyte: ion compound
contain metal that be
extracted.
Eg: Lead bromide
Observation:
Cathode: Grey metal
deposited ( lead)
Anode: Brown gas
release( bromine gas)
Explanation:
6.2
Chemical Cell
-A simple chemical cell made
up of : 2 different metals
immersed in an electrolyte &
connected to an external
circuit with wires
Movement
of
electrons
ANODE to CATHODE
Terminal negative to terminal
positive
Energy
change
The flow of electrons fr –ve
terminal to +ve terminal
through the external circuit
produce electrical energy
Chemical energy to electrical
energy
Application of Chemical cell concept in
Generating electrical energy
Natural
1.Fruits/citrus fruits eg
Source act
orange, lemon
as
2.Seawater
electrolyte 3.Potato
in chemical
cell
Anode
Cathode
1.Metal is more
electropositive (easy to loss
electron become Mg2+)
2.Magesium act as negative
terminal
1.Metal is more
electronegative( easy to gain
electron become copper
atom)
2.Copper act as positive
terminal
1.Zn is more electropositive, terminal
negative, Cu terminal positive
2.The lemon juice is acidic act as electrolyte
allows the eclectrons to get to copper.
3.The flow of electrons produce electrical
energy, the bulb is lighted up