3D_Electrolytic and Chemical Cells
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Transcript of 3D_Electrolytic and Chemical Cells
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(D) Electrolytic
andChemical Cell
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Learning Objectives:
You should be able to: Explain with examples the oxidation and reduction
reactions at the electrodes of various chemical cells.
Explain with examples the oxidation and reductionreactions at the electrodes of various electrolytic cells.
State the differences between electrolytic and chemicalcells in terms of basic structure, energy conversion andthe transfer of electrons at the electrodes.
Compare and contrast electrolytic and chemical cells
with reference to the oxidation and reduction processes. Appreciate chemical cells as a source of renewable
energy.
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Comparison of Electrolytic Cell and Chemical Cell
Electrolytic Cell Chemical Cell
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Comparison of Electrolytic Cell and Chemical Cell
Electrolytic Cell Chemical Cell
requires a source of electric
current
(uses E Energy)
does not requires a source of
electric current
(releases E Energy)
electrode may be of the
same material eg Carbon
electrode must be of two
different metals
electrical energy
chemical energy
chemical energy
electrical energy
electron flow from thepositive electrode(anode) to
the negative electrode
(cathode)
electrons flow from themore electropositive metal
(negative terminal) to the
less electropositive
metal(positive terminal)
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Oxidation & Reduction in Electrolytic Cells
Electrolysis of Molten lead (II) bromide, PbBr2
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Oxidation & Reduction in Electrolytic Cells
Electrolysis of Molten lead (II) bromide, PbBr2Anode Cathode
Br lose e to become Br2(g) Pb2+ gain e to become Pb(s)
2Br(l) Br2(g) + 2e(1) ( 0 )
Pb2+(l) + 2e Pb(s)
(+2) ( 0 )
Br are oxidized to Br2
(Oxidation)
Pb2+ are reduced to Pb
(Reduction)
Br acts as reducing agent Pb2+ acts as oxidizing agent
Electrons transfer from reducing agent to oxidizing agent
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Oxidation & Reduction in Electrolytic Cells
Electrolysis of Potassium Iodide solution, KI
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Oxidation & Reduction in Electrolytic Cells
Electrolysis of Potassium Iodide solution, KI
Anode Cathode
I lose e to become I2(aq) H+ gain e to become H2 (g)
2I
(aq) I2(aq) + 2e(1) ( 0 )
2H+(aq) + 2e H2(g)
(+1) ( 0 )
I are oxidized to I2
(Oxidation)
H+ are reduced to H2
(Reduction)
I acts as reducing agent H+ acts as oxidizing agent
Electrons transfer from reducing agent to oxidizing agent
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Oxidation & Reduction in Chemical Cells
Zinc stripCopper strip
Anode Cathode
Zinc act as negative
terminal
Copper acts as positive
terminal
Oxidation Half-equation:
Zn(s) Zn(aq) + 2e
Reduction Half-equation
Cu2+(aq) + 2e Cu(s)
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For both Electrolytic and Chemical Cells
The electrode at which oxidation occurs is
called the anode.
The electrode at which reduction occurs is
called the cathode.
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Comparison of Electrolytic Cell and Chemical Cell
in terms of Redox Reaction
SimilaritiesIn both cells,
electrons are transferred from the reducing agent to the oxidizing
agent
oxidation occurs at the anode
reduction occurs at the cathode
Electrolytic Cell Chemical Cell
Differences
oxidation occurs at + electrode anode = + electrode
reduction occurs at + electrode cathode = + electrode
reduction occurs at electrode
cathode = electrode
oxidation occurs at electrode
anode = electrode
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Others Chemical Cells
There are 2 types of cells
Primary cell ----- not rechargeable
dry cell , Alkaline cell, Mercury cell
Secondary cell ----- rechargeable
nickel-cadmium cell, lead-acid accumulator
nickel metal hydride cell, lithium ion cell,
lithium polymer cell
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Practice D1. An electrolysis process of copper(II) sulphate solution
using carbon electrode has been carried out.a. State the observation obtained at
electrode A and B.
b. Write the half equation thatoccurred at each electrode
c. Determine the processes thathappened at each electrode
d. Name the
a. Oxidizing agent
b. Reducing agent
e. What is the changes of theoxidation number of copper?
f. What could be observed at theelectrodes if the experiment isrepeated using 1.0 moldm-3sodium chloride solution?
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Dry Cells ----- not rechargeable
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Alkaline Cells --- not rechargeable
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Nickel-cadmium cells ---
rechargeable
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Lead-acid accumulator ---
rechargeable
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Lithium Ion Cell( Li-ion)
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Lithium Polymer Cell (Li-Poly)
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Nickel Metal Hydride Cell (NiMH)