Lesson Slides : Chemistry Form 4 Chapter 6 Electrochemistry

1. CHAPTER 6: ELECTROCHEMISTRY
1

2. 1. ELECTROCHEMISTRY
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 A study of the inter-conversion of chemical energy
and electrical energy
 Energy change:
 In electrolysis
 break-down of substance by electricity
 electrical energy  chemical energy
 In voltaic cells
 chemical energy  electrical energy

3. 6.1 Electrolytes and Non-electrolytes
Electrolytes Non-electrolytes
•Substances that can
conduct electricity
when they are in
molten state or
aqueous solution and
undergo chemical
changes.
•Substances that
cannot conduct
electricity either in
molten state or
aqueous solution.

4. 6.1 Electrolytes and Non-electrolytes
Electrolytes Non-electrolytes
•Example:
Sodium chloride,
NaCl solution
Molten Lead (II)
bromide, PbBr2
All ionic compounds
•Example:
Naphthalene
Glucose solution
All covalent
compounds

5. 6.1 Electrolytes and Non-electrolytes
Electrolytes Non-electrolytes
• Contain freely
moving ions.
• Contain neutral molecules
•Do not contain freely
moving ions.

6. 6

7. 6.2 Electrolysis of Molten Compound
What is electrolysis?
A process whereby the ionic
compounds in molten or
aqueous state are broken down
into constituent elements by
passing electricity through them.

8. WHAT IS ELECTROLYTIC CELL?

9. BATTERY
ANODECATHODE
ELECTROLYTE
Electrode which
is connected to
the positive
terminal
Electrode which
is connected
to the negative
terminal
Electrodes

10. Molten PbBr2
Pb2+ ions, Br- ions
Pb2+Br-
ANODE
Accept electrons
Pb2+ + 2e-  Pb
CATHODE
Release electrons
2Br-  Br2 + 2e-
Ion move to.. Ion move to..
Grey solid producedBrown gas produced
Passing
electric

11. ANODE CATHODE
PbBr2
Pb 2+Br-
Release electron Accept electron
2Br-  Br2 + 2e- Pb2+ + 2e-  Pb
Pb2+ + 2Br-  Pb + Br2
2Br-  Br2 + 2e-
Pb2+ + 2e-  Pb
Half equation
Overall ionic equation

12. Factors affecting the products of
electrolysis for aqueous solution
A.Position of ions in the Electrochemical
Series
B. The Concentration of the solution
C. The type of Electrodes

13. A. POSITION IN THE ELECTROCHEMICAL
SERIES
 The lower position
of the ion in the
Electrochemical
Series, the easier
the ion to be
discharged during
electrolysis

14. Copper(II)
sulphate
solution
 The anions, OH-
and SO4
2- move
to the anode.
 OH- ions are
selectively
discharged.
 Bubbles of
colourless gas is
released.
Anode Cathode
4OH- (aq)  2H2O(l) + O2 (g) + 4e-
 The cations,
Cu2+.and H+
move to the
cathode.
 Cu2+ ions accept
two electrons.
 Brown solid is
formed at the
cathode.
Cu2+ (aq) + 2e-  Cu (s)
The overall ionic equation :
2Cu2+ (aq) + 4OH-(aq)  2Cu (s) + 2H2O(l) + O2 (g)
CuSO4 solution
Cu2+, H+,SO4
2- OH-.
A. Position in the Electrochemical Series

15. Concentrated
hydrochloric
acid
B . T H E C O N C E N T R A T I O N O F T H E S O L U T I O N
 The anions,OH-
and Cl- move to
the anode.
 Cl- ions are
selectively
discharged
because
concentration of
Cl- is higher than
OH-
 Bubbles of
greenish yellow
gas is produced.
2Cl- →Cl2+ 2e
Anode Cathode
 The cations,
H+ ions
move to the
cathode.
 H+ ions
accept
electron.
 Bubbles of
Colourless
gas is
produced.
2H+ + 2e →H2
The overall ionic equation :
2H+ (aq) + 2Cl-(aq)  Cl2 (g) + H2 (g)
Example : Concentrated hydrochloric acid consists of
H+, Cl-,OH-.

16. Observation :
The blue copper(II)
sulphate solution becomes
light blue because the
concentration of
copper(II)ions decreases.
 Cu2+.and H+
move to the
cathode.
 Cu2+ ions
selectively
discharged
because Cu2+is
lower than H+
in ECS
 Brown
deposit/solid is
produced
Cu2+ + 2e → Cu
Carbon Carbon
C . T H E T Y P E O F E L E C T R O D E S ( C A R B O N E L E C T R O D E S )
 OH- and SO4
2-
move to the
anode.
 OH- ions are
selectively
discharged due
to the lower
position in ECS.
 Bubbles of
colourless gas is
released at the
anode.
4OH-  2H2O + O2
+ 4e-
Anode CathodeUsing Carbon Electrode
The overall ionic equation :
2Cu2+ (aq) + 4OH-(aq)  2Cu (s) + 2H2O(l) + O2 (g)

17. Observation :
The blue colour
copper(II) sulphate
solution remains
unchanged because the
rate of discharge of
Cu2+ ions at cathode is
equal with the rate of
formation of Cu2+ at
anode.
 Cu2+.and H+
move to the
cathode.
 Cu2+ ions
selectively
discharged
because Cu2+
is lower than
H+ in the
Electochemical
Series
 Brown solid
deposit/
produced
Cu2+ + 2e- → Cu
Copper Copper
C . T H E T Y P E O F E L E C T R O D E S ( C O P P E R E L E C T R O D E S )
 Copper : active
electrode.
 Copper
electrode
dissolved and
release
electrons to
form copper(II)
ion.
 Copper
electrode
becomes
thinner// Size
of anode
decreaces
Cu → Cu2+ + 2e-
Anode Cathode
Using Copper Electrode

18. LEARNING OUTCOMES :
1 . State the uses of electrolysis in industries
2 . Explain the extraction, purification and electroplating of
metals involving electrolysis in industries.
3 . Write chemical equations to represent the electrolysis in
industries.
4 . Justify uses of electrolysis in industries
5 . Describe the problem of pollution from electrolysis in
industry.
6.4 Evaluating electrolysis
in industry
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19. Electrolysis in industries
 There are many industrial application of electrolysis
 Most common applications are as follows :
1) Extraction of metals
2) Purification of metals
3) Electroplating of metals
 Very reactive metals can only be extracted from
their ores by electrolysis.
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20. The main source of aluminium is bauxite ore (Aluminium Oxide),
the melting point of aluminium oxide is very high (over 2 000°C),
Cryolite (Na3AIF6) is added to lower the melting point to 980oC.
[Sodium fluoaluminate /aluminofluoride]
A. Extraction of Aluminium
Anode : 2O2-  O2 + 4e
Cathode : Al3+ + 3e  Al
INDUSTRIAL APPLICATIONS OF ELECTROLYSIS
(electrolyte)
•Liquid aluminium is denser than the electrolyte
•Collected at the bottom

21. Purification of Metals
 Metals extracted from their ores may contain
other metals as impurities.
 Electrolysis can be used to purify these metals
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HOW?
1. The impure metal is used as anode.
2. The pure metal is used as cathode.
3. The electrolyte is a solution containing the
ions of the metal to be purified.

22. B. Purification of Copper
The impure copper plate is connected to the +ve terminal anode.
The pure copper plate is connected to the –ve terminal cathode.
The electrolyte : copper(II) sulphate solution.
Anode : Cu  Cu2+ + 2e
Cathode : Cu2+ + 2e  Cu
Pure
cooperDeposit at
the bottom
of the
beaker

23. Electroplating of metals :
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• A process of depositing/coating a layer of metal on
another substance using electrolysis.

24. Electroplating of metals :
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1. To prevent corrosion.
2. To improve appearance.

25. THREE CONDITIONS IN ELECTROPLATING
OF METALS
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1. The anode is the electroplating metal.
2. The cathode is the object to be electroplated.
3. The electrolyte is a solution that contains
the electroplating metal ions.
Copper

26. Coating with a Thin Protective Layer of Metal.
C. Electroplating
Anode : Cu  Cu2+ + 2e
Cathode : Cu2+ + 2e  Cu
Dissolves/
becomes thinner
Coated/
deposit layer of
brown solidBlue
solution
remains
unchanged
Copper

27. Exercise page 88
27
 __________ acts as anode whereas the
__________ acts as the cathode. Both ________
and __________ are immersed in
_______________ solution.
 At the anode, ______________.
Half equation : _________________
Observation : ___________________.
 _______ and _______ ions move to the cathode
where _______ ion is selectively discharged.
Half equation : __________________
Observation : ___________________.

28. Exercise page 88
28
 Silver acts as anode whereas the iron key acts as
the cathode. Both silver and iron key are
immersed in silver nitrate solution.
 At the anode, silver ionises.
Half equation : Ag Ag+ + e-
Observation : Silver becomes thinner.
 Ag+ and OH- ions move to the cathode
where Ag+ ion is selectively discharged.
Half equation : Ag+ + e- Ag
Observation : The key is plated with grey solid.

29. 29
Harmful effects
of electrolysis
process
in industries.
The electrolysis
processes involve
high usage of
electricity
The toxic
waste pollute
water
sources
The electrolytes
used cause
environmental
pollution.

30. Harmful effects of electrolysis process in industries.
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1. The electrolysis processes involve high usage of
electricity.
 For example, recycling of aluminium requires only
9% of the electrical energy used to produce the
same quantity of aluminium in electrolysis
2. The electrolytes used cause environmental
pollution.
 In silver electroplating, potassium silver cyanide,
KAg(CN)2 solution is sometimes used as
electrolyte. The waste chemical of the electrolyte
contains cyanide ions which are toxic.
3. The toxic waste pollute water sources.
 Metal objects to be electroplated are cleaned by
acids to remove the layer of metal oxide on the
surface before electroplating. The used acid wastes
will pollute water in the drains, rivers and lakes thus
destroying aquatic life.

31. S t u d e n t s s h o u l d b e a b l e t o :
1 . Describe the structure of a simple voltaic cell and
Daniell cell
2 . Explain the production of electricity from a simple
voltaic cell
3 . Explain the reactions in a simple voltaic cell and Daniell
cell
4 . Compare and contrast the advantages and
disadvantages of various voltaic cell.
5 . Describe the difference between electrolytic cell and voltaic
cell
Learning Outcomes :
31

32. S t u d e n t s s h o u l d b e a b l e t o :
1 . Describe the structure of a simple voltaic cell and
Daniell cell
2 . Explain the production of electricity from a simple
voltaic cell
3 . Explain the reactions in a simple voltaic cell and Daniell
cell
4 . Describe the principles used in constructing the
electrochemical series
5 . Construct the electrochemical series
Learning Outcomes :
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33. 33
Voltaic Cells

34. Voltaic Cells [Galvanic Cell]
A simple voltaic cell is a cell with two different
metals being immersed into an electrolyte and
connected by wire to a voltmeter
It converts chemical energy to electrical energy.
Copper Copper
METAL A
METAL B
ELECTROLYTE
V

35. Spot the differences . . .
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Electrolytic cell Voltaic cell
anode
cathode
cathodeanode
Electrical
Energy
Chemical
Energy
Chemical
Energy
Electrical
Energy

36. Simple Voltaic Cell –
Which one is anode/cathode?
Copper Copper
Magnesium
Copper
Sodium chloride,
NaCl solution
V
 Based on the Electrochemical Series (ECS)
 Higher position, More electropositive
 Higher tendency to donate electrons
 Magnesium atom will donate electrons
Mg (s) Mg2+ (aq) + 2e-

37. Simple Voltaic Cell –
Which one is anode/cathode?
Copper CopperMagnesium Copper
Sodium chloride,
NaOH solution
V
 The flow of e- from the Magnesium ribbon to the Copper
plate results in the flow of electric current
The electrons accumulate at the surface of the Mg to the Cu
producing electricity

38. Simple Voltaic Cell –
Which one is anode/cathode?
Copper CopperMagnesium Copper
Sodium chloride,
NaOH solution
V
 When NaOH solution is used as electrolytes, what ions are
present? (H+, Na+, Mg2+ ions move towards the Cu metal)
 H+ ions will accept electrons from Cu metal and be
discharged – lower position in ECS
 Hydrogen gas, H2 will be produced
H+ (aq) + 2e- H2 (g)

39. Mechanism of simple voltaic cell
Anode (Negative Terminal) Cathode (Positive Terminal)
more electropositive metal in ECS Less electropositive metal in ECS
Release electrons Accept electrons
Electrons are flow through the external circuit towards the copper plate.

40. Voltaic Cells [Daniell Cell]
 A Daniell cell is an example of voltaic cell.
 A Daniell cell is a cell with a copper metal and zinc
metal as electrodes. - copper metal as the positive
terminal and zinc metal as negative terminal.
The metals are immersed in solution of its own ions -
zinc metal immersed in the zinc sulphate solution and
the copper metal is immersed in the copper(II) sulphate
solution.
.

41. Voltaic Cell / Galvanic Cell / Chemical Cell
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41 Simple voltaic cell  Daniell cell

42. o The two solutions are separated by the porous pot/salt bridge
o A salt bridge is made from a filter paper soaked in a
saturated solution that will not react with the two electrolytes.
o The common electrolyte used are or a solution of sodium or
potassium salts.
1.Daniell cell using a
porous pot
2. Daniell cell using a
salt bridge

43. 43
Bromine
Iron (II)
Sulphate,
FeSO4
solution
Carbon electrodes
Sulphuric acid : to allowed movement of ion and to
complete the circuit.
U-Tube
e-
e-
Galvanometer
G
- +
3. U-tube

44. Functions of
salt bridge or porous pot :
(a) To prevent the two electrolytes
from mixing.
(b) To allow the flow of ions so that
the electric circuit is completed.

45. Mechanism of Daniell Cell
Anode Cathode
Electrode becomes thinner Electrode becomes thicker
Metal releases electrons
Zn Zn2+ + 2e-
Metals accept electrons
Cu2+ + 2e- Cu
The concentration of copper(II) ions decreases. The blue
colour of the solution becomes light blue// the intensity of
blue copper(II) sulphate solution decreases.
The overall ionic equation in Daniell cell is:
Zn + Cu2+ Zn2+ + Cu

46. SIMILARITIES BETWEEN AN ELECTROLYTIC
CELL AND A VOLTAIC CELL
 Consists of an electrolyte, an anode and a cathode
 Anode release electrons, Cathode receives electrons
 Electrons flow from the anode to the cathode in the external circuit
Carbon Carbon Copper Magnesium
Electrolyte
V
anode cathode anodecathode

47. DIFFERENCES BETWEEN AN ELECTROLYTIC CELL
AND A VOLTAIC CELL:
Electrolytic cell Type of cell Voltaic cell
Electrical energy 
Chemical energy
Conversion
of energy
Chemical energy 
electrical energy
From positive terminal
to negative terminal
Flow of
electrons
From negative terminal
to positive terminal
Cathode:
Accepts electrons
Negative
terminal
Anode:
Release of electrons
Anode :
Releases electrons
Positive
terminal
Cathode:
Accepts electrons
Two similar
(usually carbon) or
different metals
Types of
electrodes
Two different metals

48. Various types
of
voltaic cell
Lead acid
Accumulator
•Rechargeable
•Can be made
to have
higher voltage
Dry cell
•Portable
•Cheap
•Stable voltage
of 1.5 v
Mercury cell
Portable
Alkaline cell
•Portable
•Voltage of
1.5 V
•More long
lasting
Nickel-
cadmium
cell
•Portable
•Rechargeable
up to hundreds
of times
Advantages
•Heavy
•Expensive
•Spilled easily
•Not
rechargeable
•Not rechargeable
•Produces voltage
of 1.3 V only
•Poisonous
t
Not k
rechargeable
•Produce low
voltage of 1.25 V
•Expensive
•Heavy
Disadvantages

49. S t u d e n t s s h o u l d b e a b l e t o :
1. Describe the principles used in constructing the
electrochemical series.
2. Construct the electrochemical series.
3. Explain the importance of electrochemical series
4. Predict the ability of a metal to displace another
metal from its salt solution.
5. Write the chemical equations for metal displacement
reactions
6.6 Synthesising
electrochemical series
49

50. Electrochemical series (ECS)
 An arrangement of metals based on the
tendency of each metal atoms to donate
electrons
 The greater the tendency to donate electrons,
the more electropositive the metal,
the higher the position of metal in the ECS
50

51. The Electrochemical Series ~
The higher the position of a metal in the
electrochemical series, the greater the
ability of the metal atoms to release
electrons, and the more electropositive
the metal is.

52. 























eAgAg
2eCuCu
eHH
2ePbPb
2eSnSn
2eFeFe
2eZnZn
3eAlAl
2eMgMg
2eCaCa
eNaNa
eKK
2
2
2
2
2
3
2
2
Ability of
metal
atoms to
release
electrons
to form
ions
decreases
Ability of
cations to
accept
electrons to
form
metals
increases
Metals Cations

53. The construction of the Electrochemical Series
is based on :
1) The potential difference (V)
between two different metals
in a voltaic cell.
2) The ability of a metal to displace
another metal from its salt solution.

54. The potential difference (V) between two
different metals in a voltaic cell
 When we connect two different metals to a Voltmeter in a
voltaic cell, it will create a potential difference.
 In voltaic cell, two different metals are used to create
a potential difference, which is shown by the reading
of the voltmeter. The greater the voltage produced by
the cell, the further the two metals are in the ECS.

55. The potential difference (V) between two
different metals in a voltaic cell
 When a voltmeter shows a positive reading, the
metal that is connected to the negative terminal of
the voltmeter will be the negative terminal of the
cell. This metal is situated at a higher position in the
ECS

56. 1) THE POTENTIAL DIFFERENCE BETWEEN TWO
METALS
 In a voltaic cell, two different metals are used to create
a potential difference, shown by the reading of the
voltmeter.
* The further apart the two metals are in the
electrochemical series, the greater the voltage
produced by the cell.
Metal A Metal B
Electrolyte
V

57. EXPERIMENT 6.7
TO CONSTRUCT THE ELECTROCHEMICAL
SERIES BASED ON POTENTIAL DIFFERENCES
BETWEEN METALS
Atoms of different metals have different tendencies to
donate electrons. When two different metals are dipped
into an electrolyte, the more electropositive metal will donate
electrons first.
(more electropositive = greater tendency to donate
electrons) The more electropositive metal will become the
negative terminal (anode)

58. Example :
Figure below shows the cell voltages of a few voltaic cells
using different metals as electrodes.
Predict the negative terminal, positive terminal and cell
voltage of the following voltaic cells.
Voltaic cells Negative terminal Positive terminal Cell voltage/V
Mg/Ag
Mg/Zn
Zn/Pb
Magnesium
Magnesium
Zinc
Zinc
Lead
Silver 3.0 + 0.5 = 3.5
3.0 – 1.1 = 1.9
1.1 – 0.4 = 0.7

59.  The metal which is higher in the electrochemical series will
be the negative terminal (anode – release electrons).
 The metal which is lower in the electrochemical series will
be the positive terminal (cathode – receives electrons)
 Electrons flow from negative to positive metal through
the external circuit.

60. Magnesium strip
Copper strip
V
Copper(II) sulphate,
CuSO4 solution
Voltmeter
Electron flow
Mg Mg2+ + 2e
Cu2+ + 2e Cu
Overall ionic equation : Mg + Cu2+ Cu + Mg2+
Showing the flow
of electrons

61. The construction of the Electrochemical Series
is based on :
1) The potential difference (V) between
two different metals in a voltaic cell.
2) The ability of a metal to
displace another metal from its
salt solution.

62. 2) The ability of a metal to displace another
metal from its salt solution
 A metal which is higher in the
electrochemical series is able to
displace a metal below it in
the electrochemical series
from its salt solution.
 Example :
Zinc can displace copper from
copper(II) sulphate solution.
Zn + CuSO4 Cu + ZnSO4

63. The ability of a metal to displace another
metal from its salt solution
• If metal M can displace metal N from aqueous N
salt solution, then :
1) Metal M is placed higher position than
metal N in the ECS
2) Metal M is more electropositive than
metal N
3) Metal M is more likely to release electrons
than metal N
 If metal P is immersed in aqueous Q ions solution
and no reaction takes place, then the metal P is
lower position than metal Q in ECS

64. What is salt solution?
 A salt is a compound formed when the hydrogen
ion, H+ from an acid is replaced by a metal ion or an
ammonium ion, NH4
+
Acid General name of salts Example of salts
Hydrochloric acid,
HCl Chloride salts
NaCl, KCl, CuCl2, ZnCl2,
NH4Cl
Nitric acids,
HNO3 Nitrate salts
NaNO3, KNO3, Mg(NO3)2,
Pb(NO3)2, NH4NO3
Sulphuric acids,
H2SO4 Sulphate salts
Na2SO4, K2SO4, FeSO4,
CaSO4, (NH4)2SO4
Carbonic acids,
H2CO3 Carbonic salts
Na2CO3, CaCO3, MgCO3,
ZnCO3, PbCO3

65. The importance of the electrochemical series
1. To determine the terminals of voltaic
cells
2. To compare the standard voltage of the
voltaic cell
3. To predict the ability of metal to displace
another metal from its salt solution

66. The importance of the electrochemical series
1. To determine the terminals of voltaic cells
 When two different metals connected by wires and
then immersed in the electrolyte, a simple voltaic
cell is formed. The metal that is placed at a higher
position in the ECS will become the negative
terminal of the cell. The metal placed lower in the
ECS will become the positive terminal of the cell.
 Example, Zn/Cu simple voltaic cell. Zn is the negative
terminal because Zn is above Cu in ECS

67. The importance of the electrochemical series
1. To compare the standard voltage of the
voltaic cell
 The further the distance between two metals in the
ECS, the greater the cell voltage will be.
 Example, the distance between Mg and Cu is further
than that between Zn and Cu. Hence the cell voltage
produced by Mg/Cu is greater than that of Zn/Cu.

68. The importance of the electrochemical series
1. To predict the ability of metal to displace
another metal from its salt solution
 A metal that is at a higher position in the ECS can
displace another metal that is lower than itself in the
ECS from its salt solution.
 Example, Al is above Fe in the ECS. Hence Al can
displace Fe from FeSO4

69. EXPERIMENT 6.7
TO CONSTRUCT THE ELECTROCHEMICAL
SERIES BASED ON POTENTIAL
DIFFERENCES BETWEEN METALS

70. S t u d e n t s s h o u l d b e a b l e t o :
1. Justify the fact that the electrochemical industries
can improve the quality of life,
2. Describe the problem of pollution caused by the
industrial processes involving electrolysis,
3. Justify the need to dispose of waste from
electrochemical industries in a safe and orderly
manner,
4. Practice safe and systematic disposal of used
batteries.
6.7 Develop awareness and responsible
practices when handling chemicals
used in electrochemical industries
70

71. Electrochemical industries play an important role
in our daily life by improving our quality of life.
o Useful metals – Al, Na, Mg – are extracted from their
compounds or minerals from electrolysis.
o Useful chemical substances – Cl, NaOH – manufactured on
a large scale using electrolysis

72. Electrochemical industries play an important role
in our daily life by improving our quality of life.
o Electroplating of iron with chromium to protect the iron
components of machinery from corrosion. Silver plating is
commonly used in the making of fine cutleries
o Various voltaic cells are used in different devices – radio,
torchlight, handphones

73.  However, a safe and systematic method of disposal of used
batteries and industrial by-products in electrochemical
industries is important to prevent environmental pollution
 Used batteries should be separated from other household disposal. They
are required to be disposed off separately to prevent the chemicals of the
batteries from leaking and polluting water sources.
 Parts of the batteries that are useful should be recycled

74.  Chemical wastes from electrolytic industries should be treated to remove
the poisonous chemicals before being disposed as industrial waste
 Acids that are used to clean metals before electroplating should be diluted and
neutralised before draining off as waste water
 Metal ions that are toxic and hazardous to human health such as cadmium ion,
chromium ion and nickel ion need to be treated and removed from industrial
effluent

75. The importance and effects of electrochemical
industries
 Oxygen gas, chlorine gas can be produced by
electrolysis.
 Electroplating are widely used to prevent
corrosion and enhance the appearance of the
materials.
 The industrial manufacture of batteries produces
various types of cells and batteries in different shapes
and sizes.

76. The pollution caused by the electrochemical
industries are as follows:
• The electroplating industries produce pollutants
such as poisonous heavy metal ions and poisonous
cyanide ions.
• The use of mercury electrodes in electrolysis can
cause air and water pollution.
• Thus, the waste should be treated and
disposed of in a safe and orderly manner.

77. Voltaic Cells [Galvanic Cell]
 A Daniell cell is an example of voltaic cell.
A Daniell cell is a cell with a copper metal and zinc metal as
electrodes. - copper metal as the positive terminal and zinc metal
as negative terminal.
The metals are immersed in solution of its own ions - zinc metal
immersed in the zinc sulphate solution and the copper metal is
immersed in the copper(II) sulphate solution.
.
Copper Copper
METAL A METAL B
ELECTROLYTE
V