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Chapter 6
Electrochemistry
A. Electrolytes & Non-electrolytes
Electrolytes
Substances that can conduct electricity and
undergo chemical changes
Non-e...
Electrolyte
Non-electrolyte
Why electrolyte at molten and aqueous state
can conduct electricity?
BECAUSE
There presence of free moving ions in the
ele...
B. Electrolysis of Molten Compounds
Electrolysis
A process where compounds in molten or
aqueous state are broken down into...
Electrolytic cell
The set of apparatus needed to conduct
electrolysis
Electrolyte
CathodeAnode
+ -
STEPS OCCUR DURING
ELEC...
Important note: Observation
Anode (positive electrode)
Electrolysis product Observation Confirmatory test
Chlorine gas Gre...
Important note: Observation
Cathode (negative electrode)
Electrolysis product Observation Confirmatory test
Almost all met...
Electrolysis of molten compound
Electrolysis of molten compound
• PbBr2
• LiCl
• MgBr2
• PbI2
• ZnO
• CuCl2
• Molten Potassium oxide
• Molten Magnesium ox...
Electrolysis of Aqueous Solutions
Factors that affect the electrolysis of an
aqueous solution
• Position of ions in the El...
Position of ions in
the Electrochemical Series
• The ions that are lower in the electrochemical
series will be selected di...
K+
Na+
Ca2+
Mg2+
Al3+
Zn2+
Fe2+
Sn2+
Pb2+
H+
Cu2+
Ag+
F-
SO4
2-
NO3
-
Cl-
Br-
I-
OH-
The Electrochemical Series
Ease of di...
0.01 mol dm-3 of copper(II) sulphate
using carbon as electrodes
1 mol dm-3 of
copper(II) sulphate
solution
CarbonCarbon
Concentration of ions
• If the concentration of a particular ions is
high, the ions is selectively discharged
TIPS:
ANODE
...
2 mol dm-3 of hydrochloric acid, HCl
using platinum as electrodes
2 mol dm-3 of
hydrochloric acid, HCl
PlatinumPlatinum
Anode :
Cathode :
Types of electrodes
• Electrolysis of copper(II) sulphate, CuSO4
solution using copper electrode
• Electrolysis of silver ...
0.02 mol dm-3 of copper(II) sulphate, CuSO4
using copper as electrodes
0.02 mol dm-3 of
copper(II) sulphate,
CuSO4
CopperC...
Anode :
Cathode :
0.02 mol dm-3 of silver nitrate, AgNO3
using silver as electrodes
0.02 mol dm-3 of silver
nitrate, AgNO3
SilverSilver
D. Electrolysis in Industries
• The most industrial application of electrolysis:
1. extraction
2. purification
3. electrop...
E. Voltaic Cells
• Chemical energy to electrical energy
• Examples of chemical cell:
 simple voltaic cell
 Daniell cell
...
Simple Voltaic Cell
Two different metals being immersed into an
electrolyte and connected by wire
V
Daniell cell – has two types
• Use porous pot
• Use salt bridge
Use porous pot
Use salt bridge
F. The Electrochemical Series
• The Electrochemical Series is series of
element, arranged according to the order of
decrea...
Principles Used:
• Metals are arranged according to the tendency of
their atoms to release electron.
• More the tendency o...
The Electrochemical Series can be
constructed based on:
Metals are arranged according to their tendency
to release electro...
The ability of a metal to displace another metal
from its salt solution.
• If metal is able to displace another metal
from...
The potential difference between two metals.
• The further apart between two metals in
the Electrochemical Series, the gre...
Chapter 6 Electrochemistry
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Chapter 6 Electrochemistry

Chapter 6 Electrochemistry

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Chapter 6 Electrochemistry

  1. 1. Chapter 6 Electrochemistry
  2. 2. A. Electrolytes & Non-electrolytes Electrolytes Substances that can conduct electricity and undergo chemical changes Non-electrolytes Substances that cannot conduct electricity
  3. 3. Electrolyte Non-electrolyte
  4. 4. Why electrolyte at molten and aqueous state can conduct electricity? BECAUSE There presence of free moving ions in the electrolyte
  5. 5. B. Electrolysis of Molten Compounds Electrolysis A process where compounds in molten or aqueous state are broken down into their constituent elements by passing electricity through them
  6. 6. Electrolytic cell The set of apparatus needed to conduct electrolysis Electrolyte CathodeAnode + - STEPS OCCUR DURING ELECTROLYSIS  Movement of ions to the electrodes.  Discharges of ions at the electrodes. Graphite or platinum is usually used as electrodes because they are inert.
  7. 7. Important note: Observation Anode (positive electrode) Electrolysis product Observation Confirmatory test Chlorine gas Greenish-yellow gas bubbles released Place moist blue litmus paper into test tube Moist blue litmus paper turn redBromine gas Brown gas released Iodine Purple gas released Oxygen gas Colourless gas bubble released Place a glow wooden splinter near the mouth of test tube The glowing wooden splinter light up Metal (all metal) The mass of electrode decreased Copper metal Brown solid formed
  8. 8. Important note: Observation Cathode (negative electrode) Electrolysis product Observation Confirmatory test Almost all metal (except copper metal) Grey solid formed The mass of electrode increase No test for metals Copper metal Brown solid formed Hydrogen gas Colourless gas bubbles released Place a lighted wooden splinter near the mouth of test tube A “pop” sound heard/produced
  9. 9. Electrolysis of molten compound
  10. 10. Electrolysis of molten compound • PbBr2 • LiCl • MgBr2 • PbI2 • ZnO • CuCl2 • Molten Potassium oxide • Molten Magnesium oxide • Molten Potassium iodide
  11. 11. Electrolysis of Aqueous Solutions Factors that affect the electrolysis of an aqueous solution • Position of ions in the Electrochemical Series • Concentration of ions in the electrolytes • Types of electrodes used in the electrolysis
  12. 12. Position of ions in the Electrochemical Series • The ions that are lower in the electrochemical series will be selected discharged
  13. 13. K+ Na+ Ca2+ Mg2+ Al3+ Zn2+ Fe2+ Sn2+ Pb2+ H+ Cu2+ Ag+ F- SO4 2- NO3 - Cl- Br- I- OH- The Electrochemical Series Ease of discharge increases
  14. 14. 0.01 mol dm-3 of copper(II) sulphate using carbon as electrodes 1 mol dm-3 of copper(II) sulphate solution CarbonCarbon
  15. 15. Concentration of ions • If the concentration of a particular ions is high, the ions is selectively discharged TIPS: ANODE Ion selectively discharged based on CONCENTRATION of ions CATHODE Ion selectively discharged based on position of ions in Electrochemical Series
  16. 16. 2 mol dm-3 of hydrochloric acid, HCl using platinum as electrodes 2 mol dm-3 of hydrochloric acid, HCl PlatinumPlatinum
  17. 17. Anode : Cathode :
  18. 18. Types of electrodes • Electrolysis of copper(II) sulphate, CuSO4 solution using copper electrode • Electrolysis of silver nitrate, AgNO3 solution using silver electrode
  19. 19. 0.02 mol dm-3 of copper(II) sulphate, CuSO4 using copper as electrodes 0.02 mol dm-3 of copper(II) sulphate, CuSO4 CopperCopper
  20. 20. Anode : Cathode :
  21. 21. 0.02 mol dm-3 of silver nitrate, AgNO3 using silver as electrodes 0.02 mol dm-3 of silver nitrate, AgNO3 SilverSilver
  22. 22. D. Electrolysis in Industries • The most industrial application of electrolysis: 1. extraction 2. purification 3. electroplating of metals
  23. 23. E. Voltaic Cells • Chemical energy to electrical energy • Examples of chemical cell:  simple voltaic cell  Daniell cell  dry cell  alkaline cell  lead-acid accumulator
  24. 24. Simple Voltaic Cell Two different metals being immersed into an electrolyte and connected by wire V
  25. 25. Daniell cell – has two types • Use porous pot • Use salt bridge
  26. 26. Use porous pot
  27. 27. Use salt bridge
  28. 28. F. The Electrochemical Series • The Electrochemical Series is series of element, arranged according to the order of decreasing tendency to released electrons. • Or the greater the tendency to donate electrons, the more electropositive is the metal and the higher it is in the Electrochemical Series.
  29. 29. Principles Used: • Metals are arranged according to the tendency of their atoms to release electron. • More the tendency of their atoms to release electron, the higher located it is in the series. • Elements located at HIGHER part of the Electrochemical Series are more electropositive and have higher tendencies to release electrons to form positive ions. • Example : magnesium is more electropositive than copper in Electrochemical Series
  30. 30. The Electrochemical Series can be constructed based on: Metals are arranged according to their tendency to release electrons to form positive ion (cation). • metal has a higher tendency to release electron placed a the higher position in Electrochemical Series. • the metal act as negative terminal
  31. 31. The ability of a metal to displace another metal from its salt solution. • If metal is able to displace another metal from its salt solution, this metal is placed at the higher position in Electrochemical Series
  32. 32. The potential difference between two metals. • The further apart between two metals in the Electrochemical Series, the greater the potential difference between them. • The greater the voltage produced by the cell.

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