Electrochemistry 12 _ Class Notes __ Parishram 2025.pdf

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1. —2025—
FOR CLASS 127”

Chemistry

Electrochemistry
(Lecture - mt

By- Bharti Ma’am

®

lá

E. +

2. TOPICS .......,

@ Kohlxausch Law
©) Cond: -+

© dry

O) Rurng af Fe

3. CHAPTER NAM

3

A
Electrochemistry

nt
2

pe
ve

Er STE 4, D
ME lag ES = A

u,

4. Quick Revision

R=f2 E £
% 2 Ay E = Sen = Cert mil
I M mol) à
Fa em
f RE er ae,
A = O
Ke pak Kxlooo _ Soa à She

LL i
= N ey
S m ;

5. Chick Revision PR
®

Im = loocm

ey = Speutre neh:

Im x im = loo com x lowe"

mt = loom yy

O) Conducnity dec], (Rate of Flow
É Deer J Im, Neg, y Conductance Ene?

Resistviry= Sheutre Resiste,

Upon Pilutim
Le un

6. a iat th
BEIN HA = H° +A E "Treagent)
ue dE dx + ca
n° d=0 c o 6
= ” ZU)
hy = Mole Conduttivirg Lz ENG Ck = AA
ok tone ‘ce? de =) a
Da = Molar cones Km Io
at Cont 2040 Ney ye,

OR
We an

8. Problem 1: Firstly, passing direct current (DC) changes the composition of the solution.

Solution1: Wewe AC dc RC ui not Change The Compositon,

Of Electrolyte
Problem 2: Secondly, a solution cannot be connected to the bridge like a metallic wire or
other solid conductor. oe
nn

Solution 2: The second problem is solved by using a specially designed vessel called

conductivity cell.
Bel Lg Unknown ‘Rea:

Based on wheat stone bridge principle, standard solution of KCI is used [K of KCl is
taken]. “+= 8

9. Experiment (1)

Kxa > Known Y

10. Ro,

ANS

Ry

|
ute So y i
+ Elect roly ae

11. YO Y
O
Resistance of a conductivity cell filled with 0.1 mol L-! KCI solution is 1000. If the
resistance of the same cell when filled with 0.02 mol L-! KCl solution is 520 0. Calculate

the conductivity and molar conductivity of 0.02 mol L-! KCI solution. The conductivity of
a mer
0.1 mol L-! KCI solution is 1.29 S/m. R= Bao kz?

= = 1129 =
Rz bon K Sr [= 0:02 mafLit font
Pa esmas | x
; Berl 4 A RE
K=lx2 : > OY Sot ne
OR 52 Y
KKR tA Neen KK 1000 A
rex ve À N

eae ; Y
AA i 697

12. The electrical resistance of a column of 0.05 mol L-! NaOH solution of diameter 1 cm
and length 50 cm is 5.55 x 103 ohm. Calculate its resistivity, conductivity and molar
conductivity.

YY

13. At infinite dilution ions move freely, that means movement of ions doesn't depend upon
the presence of co-ions (i.e. cations and anions).
ig conductivity of an electrolyte at infinite dilution is sum of molar conductivities of
its constituent ions in the electrolyte.

14. o = 0
e. CCH, cook) A (ayer r 4, (4)
N Cea) * N, :
m(CH one)” Y A (Naxa) = 2
SoY y :
= a ES 13 na? Nel + ce

IM =
CE) ” ae

SY

15. 0 _y i
2 N (Moro = A py NG) me)

men (toos * ¿ Nn bie 2
Nate wD G. dE

N
an LNH H) = 5 +2 -X

Ñ

\

16. - 2
A ma Su
Co.) © 4
e 4
Calculate A°,, for CaCl, and MgSO,

A°/(S cm? mol-!) A°/(S cm2 mol-!)

17. su
(0) Am (ca) = i (cat) AN (ex)

® Am Crryses) = N $) + Anti)

Cm)

O

18. . Suede:
of hal je Cul annan ed i
No vay u n Su

19. In the primary batteries, the reaction occurs only once and after use over a period of

time battery becomes dead and cannot be reused again.
PR

after its

The most familiar example of this type is the dry cell|(known as Leclanche cell

discoverer) which is used commonly in our transistors and [clocks]

20. In the primary batteries, the reaction occurs only once and after

use over a period of time battery becomes dead and [cannot be

reused again.

The most familiar example of this type is the dry cell (known as
Leclanche cell after its discoverer) which is used commonly in
our transistors and clocks.

Y
ont Anode : Zn(s) > Zn?* +2e-
Cathode : MnO, + NH,* + e” >|MnO(OH)
(Y) Ge >

der inasCRed”)’

And >am cup

+

NH,

Any coh

'arbon rod
(cathode)

Zinc cup MnO, +
(anode) carbon black
+ NH,CI paste

21. Mercury cell, suitable for|low current devices like hearing aids, watches, etc. consists of
zinc - mercury amalgam as anode and a paste of HgO and carbon as the cathode. The
electrolyte is a paste of KOH and ZnO

0 te .
Anode : Zn(Hg) + 20H > ZnO(S) + H,O + 2e- joa Me im vs)
Cathode : HgO + H,O + 2e- > Hg(I) + 20H-

G 5 n
+ <A da (Red y)

Emp = kame Separator Cathode C°1! an
G ashore Aguda and Sip

22. A secondary cell after use can be recharged by passing current through it in the

opposite direction so that it can be used again.

A good secondary cell can undergo a

large number of discharging and charging cycles.

23. @

ah De

commonly used in automobiles and invertors. It Le lead anode and a grid of

lead packed with lead dioxide (PbO,) as cathode.| A(38%)solution of sulphuric acid is
used as an electrolyte.

ait of = ae Éledrekte

Andde: Pb(S) +$0,2-(aq) > PbSO,(S)+2e- >77: |

Cathode: PbO,(S) + SO,? (aq) + 4H*(aq) + 2e-—> PbSO,(S) + 2H,0(1)

G
En Se EN

decimos

ot,

24. ¿4 Positive plates:
lead grids filled
with PbO,

acid solution

On charging the battery the reaction is reversed and PbSO,(s) on anode and cathode is
converted into Pb and PbO,, respectively.

25. Nickel-cadmium cell has longer life| than the lead storage cell but more expensive to

manufacture Ine imo:s Ano
© IR axa 7 aU
Cd(s) + 2Ni(OH),(s) > Cd0(s) + 2Ni(OH),(s) +H,00)
+3 ed"
dec ines DOdholt

Positive plate
Separator

Negative plate

26. Heat q Chemical a Electrical
ana Envy

Galvanic cells that are designed to convert the energy of combustion of fuels like
hydrogen, methane, methanol, etc. directly into electrical energy are called fuel cells.

Reg") : dew In os à Sop AN
Cathode: 0,(g) + 2H,0(1) + 4e- > 40H-(aq) SS t

|
Anode: — 2HS(g) + 40H-(aq) > 4H,0(1) + 4e- ee
w

oud dne im os a N

27. —— fs à ao arde