Transcript media1474338146x

Electrochemical cells
Teacher: Wipawadee Budda
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Question check…... !!!!!!
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1. Reduction is a decrease in oxidation state
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8. Energy out: in galvanic cells
2. Ecell for galvanic cell is positive
3. Oxidation is the loss of electrons
4. Reduction is the gain of electrons
5. Electron transfer via salt bridge
6. Reaction at cathode is reduction
7. Anode is positive post for galvanic cell
9. Energy in: in electrolytic cells
10. Battery = Galvanic cells
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safe
One step
Ideal
process
Simple
separation
Atom-efficient
Renewable
resources
Environmental
acceptability
100% yield
Zero waste
Minimum
packaging
Care ecology
Understand
impact of all
products on
environment
Ideal
user
Minimum
usage
recycle
Minimum
energy
Ideal
product
Recyclable
reusable
safe
100%
biodegradable
reuse
Fig. 1. Criteria for ideal product, process of manufacture and user
(Doble and Kruthiventi., 2007)
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ASEAN’s Energy Situation

Oil

Natural Gas

Alternative Energy

Electricity
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Electricity
- Wind
- Solar
- Water
- Coal
- Nuclear
- Chemicals
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Electrochemical Cells
A system consisting of electrodes that dip into an
electrolyte and in which a chemical reaction either uses or
generates an electric current.
Figure 1: Voltaic (galvanic) cells
Figure 2: Electrolytic cells
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Question…!!!
How can you apply the principles of
electrochemical cells to generate
energy?
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Mechanism
Figure 1: Voltaic (galvanic) cells
Oxidation rxn:
Zn(s)  Zn2+(aq) + 2e-
Reduction rxn:
Cu2+(aq) + 2e- 
Redox rxn:
Zn(s) + Cu2+(aq)  Zn2+(aq) + Cu(s)9
Cu(s)
Question…!!!
As a chemical reaction can generate an
electric current.
So, Can electric current drive a
nonspontaneous reaction?
How to use it?
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Electrolytic cell
Changing in solution
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Changing at electrode (anode corroded)
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2
4
Separation
of concentrated
solution
Separation
of diluted solution
Electroplating
Metal purification
DC Power
Source
DC Power
Source
DC Power
Source
DC Power
Source
+
-
e-
+
-
+
e-
-
Ag
X+ Y-
H2O
X+
YH2O
+
e-
-
100% B
Object
XH2O Ag+ H2O
Impure
metal
Metal
(Er > B+)
e-
AC
BD
B
100%
B+
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Part 1: Fruit Battery
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sequence
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Materials
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Fruits (lemon, apple and potato)
Copper electrode
Zinc electrode
A digital or analog multimeter
Alligator clips (or Leads)
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Procedure
Insert copper and zinc electrodes into the
lemon, close but not touching each other.
Test the multimeter before the experiment,
that should show no current and no voltage.
Use Clip leads to connect our electrodes to the multimeter to measure
voltage between two electrodes or current passing through the multimeter.
Carefully record readings from the multimeter.
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Results
Type of fruit
lemon
apple
potato
The voltage
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Part 2: Electroplating
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Materials
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Copper electrode
Spoon (Stainless steel electrode)
Copper sulfate electrolyte (1.0 M CuSO4)
D.C power supply with alligator clips
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Procedure
Cathode: The metal to be covered with a new metal
Anode: Metal to be plated on top the other metal
Electrolyte: Must contain the ion of the metal that plates
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Applications
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Galvanic cells
Primary cell
Dry cell
Alkaline cell
Mercury cell
Silver cell
Fuel cells
Secondary cell
Lead-storage cell
nickel-cadmium cell
Litium-ion-polymer cell
Sodium-sulfur cell
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A Common Dry Cell Battery (Lechanche’s dry cell)
Anode:
Cathode:
Zn (s)  Zn2+ (aq) + 2e2MnO2 (s) + 2NH4+(aq) + 2e-  Mn2O3 (s) + 2NH3 (g) + H2O (l)
Overall rxn: Zn (s) + 2MnO2 (s) + 2NH4+(aq)
 Zn2+ (aq) + Mn2O3 (s) + 2NH3 (g) + H2O (l)
Electrolytic cell
Changing in solution
1
Changing at electrode (anode corroded)
3
2
4
Separation
of concentrated
solution
Separation
of diluted solution
Electroplating
Metal purification
DC Power
Source
DC Power
Source
DC Power
Source
DC Power
Source
+
-
e-
+
-
+
e-
-
Ag
X+ Y-
H2O
X+
YH2O
+
e-
-
100% B
Object
XH2O Ag+ H2O
Impure
metal
Metal
(Er > B+)
e-
AC
BD
B
100%
B+
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Copper Ring
Gold Plated