Electro chemical cells
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PRESENTATION PRESENTATION OF OF
CHEMISTRYCHEMISTRY
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PRESENTED TOPRESENTED TOMA’AM TAHIRA TARIQMA’AM TAHIRA TARIQ
PRESENTED BYPRESENTED BYHINA JABEENHINA JABEENROLL NO: 120ROLL NO: 120
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TEACHING MATERIALSTEACHING MATERIALS
White boardWhite boardDuster Duster MarkerMarkerBooksBooks
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GENERAL OBJECTIVESGENERAL OBJECTIVES
Enable the student to acquire Enable the student to acquire comprehension of chemistry.comprehension of chemistry.
To compare learnt knowledge with To compare learnt knowledge with surrounding.surrounding.
To develop interest among student To develop interest among student towards chemistry.towards chemistry.
Enable the student to apply the leant Enable the student to apply the leant knowledge.knowledge.
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SPEACIFIC KNOWLEDGE SPEACIFIC KNOWLEDGE
At the end of the topic student will be able toAt the end of the topic student will be able toSketch a Denial cell, label cathode, anode Sketch a Denial cell, label cathode, anode
and direction of the flow of electron.and direction of the flow of electron.Distinguish between electrolytic and Distinguish between electrolytic and
voltaic cell.voltaic cell. Identify half cell in which oxidation occur Identify half cell in which oxidation occur
and half cell in which reduction occur in and half cell in which reduction occur in voltaic cell.voltaic cell.
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Previous knowledgePrevious knowledge
Define electro chemical cell?Define electro chemical cell?
What are the types of electro chemical What are the types of electro chemical cell, name them?cell, name them?
Define electrolytic cell and voltaic cell?Define electrolytic cell and voltaic cell?
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INTRODUCTIONINTRODUCTION ELECTRO CHEMICAL CELL: ELECTRO CHEMICAL CELL: An arrangement An arrangement
which consist of electrodes dipped into an which consist of electrodes dipped into an electrolyte in which chemical reaction electrolyte in which chemical reaction uses/generates electric current .uses/generates electric current .
ELECROLYTIC CELL: ELECROLYTIC CELL: The electro chemical cell The electro chemical cell in which a reaction occur with the help of electric in which a reaction occur with the help of electric current.current.
VOLTAIC/GALVANIC CELLVOLTAIC/GALVANIC CELL: The electro : The electro chemical cell in which a reaction generates chemical cell in which a reaction generates electric current.electric current.
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ELECTRO-CHEMICAL ELECTRO-CHEMICAL REACTIONREACTION
We discuss electrolysis of :We discuss electrolysis of :
A) fused salt A) fused salt
B) Aqueous solution of saltB) Aqueous solution of salt
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Electrolysis of aq. sol. of SaltElectrolysis of aq. sol. of Salt Not so simpleNot so simple Reason Reason
Undergoes REDOX reaction of H2O
•Along with redox reaction of dissolved salt
•Product -------not precisely predicted
e.g. KNO3
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Electrolysis of aq. Sol of KNOElectrolysis of aq. Sol of KNO33
KNOKNO33 K+ + NO3-
H2O + H2O H3O+ + OH-
It dissociate as:
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battery+- power
source
e-
e-
KNO3 (aq)
(-) (+)cathodedifferent half-cell
Aqueous KNO3
anode
-
K+
NO3-
H2O
What could be reduced at the
cathode?
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Reaction at cathode Reaction at cathode
K+from
KNO3 Not discharge At
cathodecathode
Reason
Small concentration H3O+ & OH-
FormedBy
Dissociation of H2O
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H3O+ takes e- from cathode Formed Hº
Hº Hº
Combine
H2At Cathode
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Reaction at anode Reaction at anode
NO3-
OH-Tendency
To moveAnode
Oxidation of OH- Easier than NO3-
OH- O2 + H2Odischarge
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RESULTRESULT
KK++ & NO & NO33-- remain in solutionremain in solution Water is electrolyzed and converted into Water is electrolyzed and converted into
HH22 and O and O22
HH22O is electrolyzed in presence of KNOO is electrolyzed in presence of KNO33
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Voltaic CellsVoltaic Cells
Invented by Alessandro Volta in Invented by Alessandro Volta in 18001800
Voltaic cells:Voltaic cells: electrochemical electrochemical cells used to convert chemical cells used to convert chemical energy into electrical energyenergy into electrical energy Examples Examples flashlights or battery- flashlights or battery-
powered calculatorspowered calculators Made of Made of half cellshalf cells
One part of the voltaic cell where One part of the voltaic cell where oxidation or reduction is occurringoxidation or reduction is occurring
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VOLTAIC CELL/GALVANIC VOLTAIC CELL/GALVANIC CELL:CELL:
To understand the working of voltaic To understand the working of voltaic cell, take example of Daniel cellcell, take example of Daniel cell
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GALVANIC CELL/VOLTAIC CEL
TWO HALF CELLS
LEFT HALF CELL RIGHT HALF CELL
CONNECTED THROUGH SLT BRIDGE
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LEFT HALF CELLLEFT HALF CELL
Zn METALSTRIP
Giving equilibrium1M ZnSO4
CONTAINS
DIPPED IN
ANODE
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RIGHT HALF CELLRIGHT HALF CELL
COPPER METALSTRIP
Giving equilibrium1M Cu SO4
CONTAINS
DIPPED IN
CATHODE
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Cu
1.0 M CuSO4
Zn
1.0 M ZnSO4
CellConstruction
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Zn electrode
leavee- Cu electrode
Zn Cu
GIVING NET
+ive CHARGE
GIVING NET
-ive CHARGE
Electron External circuitflow from
Zn electrode Cu electrode
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Working of galvanic cellWorking of galvanic cell
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REDOX REACTIONREDOX REACTION
LEFT HALF CELL REACTION
RIGHT HALF CELL REACTION
REDOX
REACTION
VOLTIC CELL
REACTION
OR
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Galvanic cellGalvanic cell
cathode half-cellcathode half-cell
REDUCTIONREDUCTION CuCu+2+2 + 2e + 2e-- Cu Cu
anode half-cell anode half-cell
OXIDATIONOXIDATION Zn Zn Zn Zn+2+2 +2e +2e--
overall cell reactionoverall cell reaction
Zn + CuZn + Cu+2+2 Zn Zn+2+2 + Cu + Cu
Spontaneous reaction that produces electrical current!
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Cu
1.0 M CuSO4
Zn
1.0 M ZnSO4
Cu plates out
or deposits
on electrode
Zn electrode erodes
or dissolves
cathode half-cellCu+2 + 2e- Cu
anode half-cellZn Zn+2 + 2e-
-+
What about half-cell reactions?
What about the sign of the electrodes?
What happened
at each electrode?
Why?
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1.1V current Zn electrode
Cu electrode
to
throughExternal circuit
having
concentration 1 M solution each
Temperature = 25˚c
Reduction Cu electrode
Oxidation Zn electrode
flow
from
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Cu
1.0 M CuSO4
Zn
1.0 M ZnSO4
cathode half-cellCu+2 + 2e- Cu
anode half-cellZn Zn+2 + 2e-
-+
Now replace the light bulb with a volt meter.
1.1 volts
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SALT BRIDGESALT BRIDGE
KCL, KNO3, K2SO4
Saturated Solution of
Strong Electrolyte
Porous Ends at both sides
Sealed Glass / Wool / Cotton Plug
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Galvanic Electrolytic
Need power sourceProduces electrical current
Electric condition take place
Comparison of Electrochemical Cells
Non spontaneous redox reaction
Spontaneous redox reaction
Electrolysis take place
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QUESTIONS
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FILL IN THE BLANKSFILL IN THE BLANKS1.1. ____________of aq. Sol. of salt is not so ____________of aq. Sol. of salt is not so
simplesimple
2.2. Electrolysis of aq. Sol. of _____is not so Electrolysis of aq. Sol. of _____is not so simplesimple
3.3. KNOKNO33 < >______ +NO < >______ +NO33¯
4.4. _______< > K_______< > K++ +NO +NO33¯̄
5.5. HH22O +e< > Hº + ______O +e< > Hº + ______
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6.6. Two _______atom combine to form Two _______atom combine to form hydrogen gashydrogen gas
7.7. Hydrogen gas is formed by the Hydrogen gas is formed by the combination of two ________ atoms.combination of two ________ atoms.
8.8. OHOH¯ OH OHº + eº + e
9.9. 4OH4OH- O O2 2 +_________ +_________
10.10. In electrolysis of water, HIn electrolysis of water, H2O is converted O is converted
into_____ and _____into_____ and _____
11.11. _______ is used as electrolyte in _______ is used as electrolyte in electrolysis of Helectrolysis of H22OO
12.12. _______ cell is an example of voltaic cell_______ cell is an example of voltaic cell
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13.13. Voltaic/galvanic cell consist of _____ half Voltaic/galvanic cell consist of _____ half cellcell
14.14. Two half cell are connected through Two half cell are connected through ______________________
15.15. Right half cell contain _____ metal stripRight half cell contain _____ metal strip16.16. Left half cell contain _____ metal stripLeft half cell contain _____ metal strip17.17. Cu metal strip is dipped into 1M sol. Of Cu metal strip is dipped into 1M sol. Of
____________18.18. Zn metal strip is dipped into 1M sol. Of Zn metal strip is dipped into 1M sol. Of
____________19.19. Sum of two half cell reaction is called Sum of two half cell reaction is called
________ reaction________ reaction
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20.20. Salt bridge is _____ shapeSalt bridge is _____ shape
21.21. Salt bridge is made up of ______ tubeSalt bridge is made up of ______ tube
22.22. Tube of salt bridge is ______ at both endTube of salt bridge is ______ at both end
23.23. End of salt bridge Is made up of _____ End of salt bridge Is made up of _____ materialmaterial
24.24. _______ material hold the solution in U _______ material hold the solution in U shapedshaped
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Identify the followingIdentify the following
AnodeAnodeCathodeCathodeSalt bridgeSalt bridge
Cu Zn
-+ 1.1 volts