Chemistry

2. INTRODUCTION
 In nature different forms of energy are available.
These forms of energy are inter- convertible .
 For e g.
Electrical energy Chemical energy

3. TYPES OF CELL
1)ELECTROLYTIC CELL-
It is a cell which convert electrical energy into chemical
energy. Eg Anodising
Electrolysis –
It is a process in which non spontaneous Redox
reaction is forced to occur by passing electricity
through an electrolyte.
Electrolytes are the substances in the aqueous solution
having conductivities are higher than that of water.
For e.g. KCl, NaOH and CH3COOH.

4. Redox Reaction
 Redox reaction- It is the reaction in which oxidation
 and reduction reaction take place simultaneosly.
 Oxidation reaction in which atom or ion loses one
 or more than one electron
 For e.g Na Na+ + e-
 Mg Mg+2+ 2e-
 Reduction reaction is the reaction in which atom
 Or ion gain one or more than one electron
 For e.g Cl +e Cl-
 Cu+2 + 2e Cu

5. ANODISING

6. ELECTROLYSIS
OF MOLTEN
NaCl
A Cell consists of
two graphite
electrodes which
are dipped in
fused NaCl taken
in a container
Two electrodes
are connected to
Battery externally
by means of wire.

7. Working-
When potential is applied electrolysis of fused
NaCl take place and ionisation of NaCl take
Place. During electrolysis following reactions
Take place.
2 NaCl 2Na+ 2 Cl-
At anode At cathode
2Cl- 2Cl 2e- 2e- 2Na+ 2Na
2Cl Cl2

8. ELECTROLYSIS OF
AQUEOUS NaCl
In this process
moderately
Concentrated
aqueous NaCl
Solution is used
as an electrolyte.

9. WORKING
When potential is applied then Electrolysis of aqueous NaCl
Take place and ionisation of NaCl take place.
During electrolysis the following
Reactions take place
2NaCl 2Na+ 2Cl-
At anode At cathode
2Cl- Cl2 2e- 2Na+ 2OH- 2NaOH -
2H2O O2 4H+ 4e-

10. QUANTITATIVE ASPECTS OF
ELECTROLYSIS
 1)Calculation of electricity passed
Q= I t
Coulomb =ampere second
 2)calculations of moles of electrons passed
Moles of electrons= Q/F 1Faraday= 96500 coulombs
= Q/96500
3)calculations of moles of products
=Q Mole ratio/96500

11. Calculation of mass of product
 W=Moles of products molar mass of products
 =I t mole ratio molar mass of product
96500

12.  Problems
 1)calculate number of moles of electrons passed
When 0.8 amperes current is passed for 1 hour through
molten CaCl2?
 2)calculate mass of copper metal deposited at
Cathode during the passage of 5 amperes current
through CuSO4 solution for 90 minutes?
Given that molar mass of Cu=63.5 g/mol

13.  1) I=0.8
 t=3600sec no.of moles of electrons=
=Q/F=I*t/96500
=0.8 x3600/96500
=0.0298
2)w=? W=Z *I *t
=e *I *t/F
=20*5.0*(5400/96500)
=5.5958 g
I=5.O amperes
t= 90minute
=90x6o=5400 sec.

14. TWO ELECTROLYTIC CELLS
CONNECTED IN SERIES

17.  (1)In a certain electrolysis 0.561 g of zinc is deposited
in one cell containing ZnSO4 solution. Calculate the
Mass of copper deposited in another cell containing
CuSO4 solution in series with ZnSO4 cell.
Given that Molar masses of Zn=65.4 g/mol and
Cu=63.5 g/mol
 (2)A given quantity of electricity is passed through
two cells containing CuSO4 and AgNO3 solutions
Respectively. If 9.9x10 -4 Kg of silver and 2.9x10 -4 kg
Of Cu are deposited. Calculate molar mass of silver.
Given that molar mass of Cu= 63.5 g/mol.

18.  1)In a certain electrolysis 0.561 g of zinc is deposited in one cell
containing ZnSO4 solution. Calculate the Mass of copper
deposited in another cell containing CuSO4 solution in series
with ZnSO4 cell. Given that Molar masses of Zn=65.4 g/mol and
Cu=63.5 g/mol
Solution) Cell 1 Mole ratio= ½=o.5
Zn +2 +2e- Zn(s)
Cell2 Mole ratio=1/2=o.5
Cu +2 +2e- Cu (s)
W1/mole ratio x M1 = W2/mole ratio x M2
0.561 = W2
0.5 x65.4 0.5x63.5 W2=0.5447 g

19. Solution of Problem 2
 (2)A given quantity of electricity is passed through two cells
containing CuSO4 and AgNO3 solutions Respectively. If 9.9x10 -4 Kg of
silver and 2.9x10 -4 kg Of Cu are deposited. Calculate molar mass of
silver. Given that molar mass of Cu= 63.5 g/mol.
Solution : W1=2.9x10-4 kg Cu2+ + 2 e- Cu mole ratio=1/2=0.5
Ag+ + e- Ag mole ratio=1/1=1
W2=9.9x10-4 kg
M1=63.5 g/mol M2=?
Formula to be used
W1 = W2
M1 x(mole ratio)1 M2x(mole ratio)2
2.9x10-4 = 9.9x10 -4
63.5x0.5 M2 x 1 Answer :M2=108.38 g/mol

20. Salt bridge
Salt bridge is a U Shape glass tube containing saturated
solution of KCl or NH4NO3 in agar solution.

22. Functions of salt bridge
 It provides an electrical contacts between solutions.
And completes the electrical circuit.
 It avoids the mixing of two solutions.
 It helps in maintaining the electrical neutrality Of the
electrolytes in the 2 half cells.