1. PRESENTATION
OF
CHEMISTRY

2. PRESENTED TO
MA’AM TAHIRA TARIQ
PRESENTED BY
HINA JABEEN
ROLL NO: 120

3. TEACHING MATERIALS
 White board
 Duster
 Marker
 Books

4. GENERAL OBJECTIVES
 Enable the student to acquire
comprehension of chemistry.
 To compare learnt knowledge with
surrounding.
 To develop interest among student
towards chemistry.
 Enable the student to apply the leant
knowledge.

5. SPEACIFIC KNOWLEDGE
At the end of the topic student will be able to
 Sketch a Denial cell, label cathode, anode
and direction of the flow of electron.
 Distinguish between electrolytic and
voltaic cell.
 Identify half cell in which oxidation occur
and half cell in which reduction occur in
voltaic cell.

6. Previous knowledge
 Define electro chemical cell?
 What are the types of electro chemical
cell, name them?
 Define electrolytic cell and voltaic cell?

7. INTRODUCTION
 ELECTRO CHEMICAL CELL: An arrangement
which consist of electrodes dipped into an
electrolyte in which chemical reaction
uses/generates electric current .
 ELECROLYTIC CELL: The electro chemical cell
in which a reaction occur with the help of electric
current.
 VOLTAIC/GALVANIC CELL: The electro
chemical cell in which a reaction generates
electric current.

8. ELECTRO-CHEMICAL
REACTION
We discuss electrolysis of :
A) fused salt
B) Aqueous solution of salt

9. Electrolysis of aq. sol. of Salt
 Not so simple
 Reason
Undergoes REDOX reaction of H2O
•Along with redox reaction of dissolved salt
•Product -------not precisely predicted
e.g. KNO3

10. Electrolysis of aq. Sol of KNO3
It dissociate as:
KNO3 K+ + NO3-
H2O + H2O H3O+ + OH-

11. Aqueous KNO3 - battery
+ power
source
e-
e-
KNO3 (aq)
What could be
reduced at the
cathode? K+
NO3-
(-) (+)
cathode H2O
anode
different
-
half-cell

12. Reaction at cathode
from
+
K KNO3 Not discharge At
cathode
Reason
Small
concentration H3O +& OH-
Formed
By
Dissociation of
H2O

13. H3O + takes e- from cathode Formed Hº
Hº Hº
Combine
H2
At Cathode

14. Reaction at anode
NO3 - Tendency
Anode
OH- To move
-
Oxidation of OH -
Easier than NO3
OH - discharge
O2 + H2O

15. RESULT

-
K+ & NO3 remain in solution
 Water is electrolyzed and converted into
H2 and O2
 H2O is electrolyzed in presence of KNO3

16. Voltaic Cells
 Invented by Alessandro Volta in
1800
 Voltaic cells: electrochemical
cells used to convert chemical
energy into electrical energy
 Examples  flashlights or battery-
powered calculators
 Made of half cells
 One part of the voltaic cell where
oxidation or reduction is occurring

17. VOLTAIC CELL/GALVANIC
CELL:
To understand the working of voltaic
cell, take example of Daniel cell

18. GALVANIC CELL/
VOLTAIC CEL
TWO HALF CELLS
LEFT HALF CELL RIGHT HALF CELL
CONNECTED THROUGH
SLT BRIDGE

19. LEFT HALF CELL
CONTAINS Zn METAL
STRIP
DIPPED IN
Giving equilibrium
1M ZnSO4
ANODE

20. RIGHT HALF CELL
CONTAINS COPPER METAL
STRIP
DIPPED IN
Giving equilibrium
1M Cu SO4
CATHODE

22. Cell
Construction
Cu Zn
1.0 M CuSO4 1.0 M ZnSO4

23. leave
Zn electrode e - Cu electrode
Zn Cu
GIVING NET GIVING NET
+ive CHARGE -ive CHARGE
Electron flow from External circuit
Zn electrode Cu electrode

24. Working of galvanic cell

25. REDOX REACTION
REDOX
LEFT HALF CELL
REACTION REACTION
OR
VOLTIC CELL
RIGHT HALF CELL REACTION
REACTION

26. Galvanic cell
 cathode half-cell
REDUCTION Cu+2 + 2e-  Cu
 anode half-cell
OXIDATION Zn  Zn+2 +2e-
 overall cell reaction
Zn + Cu+2  Zn+2 + Cu
Spontaneous reaction that produces electrical current!

27. What about half-cell What about the sign of
reactions? the electrodes?
+ - Why?
cathode half-cell anode half-cell
Cu+2 + 2e-  Cu Zn  Zn+2 + 2e-
Cu Zn
plates out What electrode
or happened erodes
deposits Cu at each Zn or dissolves
on electrode?
electrode
1.0 M CuSO4 1.0 M ZnSO4

28. flow
1.1V current Zn electrode
from
to
through
External circuit Cu electrode
Reduction Cu electrode
having
Oxidation Zn electrode
concentration 1 M solution each
Temperature = 25˚c

29. Now replace the light bulb with a volt meter.
+ 1.1 volts -
cathode half-cell anode half-cell
Cu+2 + 2e-  Cu Zn  Zn+2 + 2e-
Cu Zn
1.0 M CuSO4 1.0 M ZnSO4

30. SALT BRIDGE
Strong Electrolyte
KCL, KNO3, K2SO4
Saturated Solution of
Porous Ends at both
sides
Sealed Glass / Wool / Cotton
Plug

31. Comparison of Electrochemical Cells
Galvanic Electrolytic
Produces electrical
current Need power source
Non spontaneous
Spontaneous
redox reaction
redox reaction
Electric condition Electrolysis take place
take place

32. QUESTIONS

33. FILL IN THE BLANKS
 ____________of aq. Sol. of salt is not so
simple
 Electrolysis of aq. Sol. of _____is not so
simple
 KNO3 < >______ +NO ¯ 3
 _______< > K+ +NO ¯ 3
 H O +e<
2 > Hº + ______

34.  Two _______atom combine to form
hydrogen gas
 Hydrogen gas is formed by the
combination of two ________ atoms.
 OH¯ OHº + e
 4OH- O2 +_________
 In electrolysis of water, H2O is converted
into_____ and _____
 _______ is used as electrolyte in
electrolysis of H2O
 _______ cell is an example of voltaic cell

35. 1. Voltaic/galvanic cell consist of _____ half
cell
2. Two half cell are connected through
___________
3. Right half cell contain _____ metal strip
4. Left half cell contain _____ metal strip
5. Cu metal strip is dipped into 1M sol. Of
______
6. Zn metal strip is dipped into 1M sol. Of
______
7. Sum of two half cell reaction is called
________ reaction

36. 1. Salt bridge is _____ shape
2. Salt bridge is made up of ______ tube
3. Tube of salt bridge is ______ at both end
4. End of salt bridge Is made up of _____
material
5. _______ material hold the solution in U
shaped

37. Identify the following
 Anode
 Cathode
+ 1.1 volts -
 Salt bridge
Cu Zn