PRESENTATION PRESENTATION OF OF

CHEMISTRYCHEMISTRY

PRESENTED TOPRESENTED TOMA’AM TAHIRA TARIQMA’AM TAHIRA TARIQ

PRESENTED BYPRESENTED BYHINA JABEENHINA JABEENROLL NO: 120ROLL NO: 120

TEACHING MATERIALSTEACHING MATERIALS

White boardWhite boardDuster Duster MarkerMarkerBooksBooks

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.

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.

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?

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.

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

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

Electrolysis of aq. Sol of KNOElectrolysis of aq. Sol of KNO33

KNOKNO33 K+ + NO3-

H2O + H2O H3O+ + OH-

It dissociate as:

battery+- power

source

e-

e-

KNO3 (aq)

(-) (+)cathodedifferent half-cell

Aqueous KNO3

anode

-

K+

NO3-

H2O

What could be reduced at the

cathode?

Reaction at cathode Reaction at cathode

K+from

KNO3 Not discharge At

cathodecathode

Reason

Small concentration H3O+ & OH-

FormedBy

Dissociation of H2O

H3O+ takes e- from cathode Formed Hº

Hº Hº

Combine

H2At Cathode

Reaction at anode Reaction at anode

NO3-

OH-Tendency

To moveAnode

Oxidation of OH- Easier than NO3-

OH- O2 + H2Odischarge

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

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

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

GALVANIC CELL/VOLTAIC CEL

TWO HALF CELLS

LEFT HALF CELL RIGHT HALF CELL

CONNECTED THROUGH SLT BRIDGE

LEFT HALF CELLLEFT HALF CELL

Zn METALSTRIP

Giving equilibrium1M ZnSO4

CONTAINS

DIPPED IN

ANODE

RIGHT HALF CELLRIGHT HALF CELL

COPPER METALSTRIP

Giving equilibrium1M Cu SO4

CONTAINS

DIPPED IN

CATHODE

Cu

1.0 M CuSO4

Zn

1.0 M ZnSO4

CellConstruction

Zn electrode

leavee- Cu electrode

Zn Cu

GIVING NET

+ive CHARGE

GIVING NET

-ive CHARGE

Electron External circuitflow from

Zn electrode Cu electrode

Working of galvanic cellWorking of galvanic cell

REDOX REACTIONREDOX REACTION

LEFT HALF CELL REACTION

RIGHT HALF CELL REACTION

REDOX

REACTION

VOLTIC CELL

REACTION

OR

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!

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?

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

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

SALT BRIDGESALT BRIDGE

KCL, KNO3, K2SO4

Saturated Solution of

Strong Electrolyte

Porous Ends at both sides

Sealed Glass / Wool / Cotton Plug

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

QUESTIONS

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 + ______

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

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

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

Identify the followingIdentify the following

AnodeAnodeCathodeCathodeSalt bridgeSalt bridge

Cu Zn

-+ 1.1 volts