Page 1 :
Unit
3
, Electrochemistry
, One
mark
questions
, 1. What
is
an
electrolyte?
, An
electrolyte
is
a
compound
which
conducts
electricity
either
in
its
aqueous
solution
or
in
its
molten
, state.
, e.g
Acids
HCl,
CH3COOH,
HNO3
,
Bases
NaOH,
NH4OH
,
Salts
CuSO4,
NaCl
etc
,
, 2. Define
conductivity
of
an
electrolytic
solution.
, Conductivity
of
a
solution
of
an
electrolyte
is
the
conductance
of
a
solution
placed
between
two
, electrodes
each
of
one
square
meter
area
kept
at
a
distance
of
1
meter
apart.
,
, 3. Write
the
S.I
unit
for
conductivity.
, SI
unit
for
conductivity
is
Sm-‐1.
,
, 4. Give
the
S.I
unit
for
molar
conductivity.
, Sm2
mol-‐1
,
, 5. State
Kohlrausch
Law.
, The
limiting
molar
conductivity
of
an
electrolyte
can
be
represented
as
the
sum
of
the
individual
, contributions
of
the
anion
and
cation
of
the
electrolyte.
,
, 6. Define
electrode
potential.
, The
potential
difference
developed
between
the
electrode
(metal)
and
the
electrolyte
(solution
, containing
its
own
ions)
when
both
the
metal
and
the
solution
are
in
equilibrium
is
called
electrode
, potential.
,
, 7. Define
standard
electrode
potential.
, Standard
electrode
potential
is
the
electrode
potential
when
the
concentrations
of
all
the
species
, involved
is
unity
(1M)
and
if
a
gas
is
involved
its
pressure
should
be
1
bar.
,
, 8. Write
Nernst
Equation.
, , E(, , M n+ / M), , = E o(, , M n+ / M), , -, , 0.059, 1,
, log10, n, ⎡⎣M n+ ⎤⎦, ,
, 9. State
Faradays
second
law
of
electrolysis.
, The
amounts
of
different
substances
liberated
by
the
same
quantity
of
electricity
passing
through
the
, electrolytic
solution
are
proportional
to
their
chemical
equivalent
weights.
Page 2 :
10., , 11., , 12., , 13., , 14., , Define
cell
potential.
, Cell
potential
is
the
potential
difference
between
the
two
electrodes
of
the
galvanic
cell.
,
, Define
EMF
of
the
cell.
, It
is
the
difference
between
the
electrode
potential
of
the
cathode
and
anode
when
no
current
is
, drawn
through
the
cell.
,
, What
is
Fuel
cell?
, Galvanic
cells
that
are
designed
to
convert
the
energy
of
combustion
of
fuels
like
hydrogen,
methane
, etc
directly
into
electrical
energy
are
called
fuel
cells.
,
, Give
a
method
to
prevent
rusting.
, Rusting
may
be
prevented
by
barrier
protection
like
painting,
metal
plating
etc.
,
, Write
the
relationship
between
cell
potential
and
Gibb’s
energy
,
, , 15., , Δ r G o = − nFE o cell
, , Write
the
relationship
between
equilibrium
constant
and
Eocell
, , E o cell =, , 0.059V, log K c
, n, 2
mark
questions
, , 1. What
are
redox
reactions?
Give
an
example.
, Reactions
in
which
both
oxidation
and
reduction
taken
place
simultaneously
are
called
redox
reactions.
, e.g
Zn + Cu2+ ⎯⎯, → Zn2+ + Cu
,
In
this
Zn
is
oxidised
to
Zn2+
Cu2+
is
reduced
to
Cu
,
, 2. Mention
any
two
factors
on
which
the
conductivity
of
an
electronic
conductor
depends.
, The
electronic
conductance
depends
on
, (i), The
nature
and
structure
of
the
metal
, (ii) The
number
of
valence
electrons
per
atom.
, (iii)
Temperature
(it
decreases
with
increase
in
the
temperature)
(any
two)
,
, 3. Mention
any
two
factors
on
which
the
conductivity
of
an
electrolytic
conductor
depends.
, The
conductivity
of
electrolytic
solution
depends
upon
, (i)
The
nature
of
the
electrolyte
, (ii)
Size
of
the
ions
produced
and
their
solvation.
, (iv), The
nature
of
the
solvent
and
its
viscosity.
, (iv)
Concentration
of
the
electrolyte
and
,
(v)
Temperature
(increases
with
increase
in
temperature
(any
two)
Page 3 :
4. Give
two
difference
between
the
conductivity
of
an
electronic
conductor
and
electrolytic
conductor.
,
, 1.
On
passing
direct
current
composition
of
electronic
conductor
does
not
change
but
that
of
,
electrolytic
conductor
changes.
, 2.
On
increasing
the
temperature
in
case
of
electronic
conductor
conductivity
decreases
in
case
of
,
electrolytic
conductor
conductivity
increases.
,
, 5. What
is
a
strong
electrolyte?
Give
an
example.
, A
strong
electrolyte
is
an
electrolyte
that
dissociates
completely
into
ions
at
moderate
concentrations
, of
its
aqueous
solution
, Ex:
acids
HCl,
H2SO4,
HNO3
, Base
NaOH,
KOH
, Salts
NaCl,
CuSO4
(any
salt)
,
, 6. What
is
a
weak
electrolyte?
Give
an
example.
, A
weak
electrolyte
is
an
electrolyte
that
dissociates
partially
into
ions
in
its
aqueous
solution.
, Ex:
CH3COOH,
NH4OH
,
, 7. Define
molar
conductivity.
How
is
it
related
to
conductivity?
, Molar
conductivity
of
a
solution
at
a
given
concentration
is
the
conductance
of
the
volume
V
of
a
, solution
containing
one
mole
of
electrolyte
kept
between
two
electrodes
with
area
of
cross
section
A
, and
distance
of
unit
length.
, It
is
represented
by
λm
, λm
=
kv
where
k
is
conductivity
and
v
is
volume
of
the
solution
containing
1
mole
of
the
electrolyte
,
or
, If
λm
is
in
Sm2mol-‐1
and
k
in
Sm-‐1
,
λm =, , k,
where
C
is
conc.
in
mol
L-‐1
, 1000C, ,
or
,
When
λm
is
in
S
cm2mol-‐1
and
k
is
in
Scm-‐1
,
λm =, , 1000k,
, C, ,
, 8. How
does
conductivity
of
a
solution
change
with
change
in
concentration
of
the
solution?
Give
, reason.
,
, Conductivity
of
a
solution
decreases
with
decrease
in
concentration
of
the
solution
due
to
decrease
in
, the
number
of
ions
per
unit
volume
of
the
solution.
Page 4 :
9. Define
limiting
molar
conductivity.
Write
the
relationship
between
molar
conductivity
and
limiting
, molar
conductivity.
, Limiting
molar
conductivity
is
the
molar
conductivity
of
a
solution
when
concentration
approaches
zero
, or
molar
conductivity
at
infinite
dilution.
, 1, , λm = λo m - AC 2
where
λ m
is
molar
conductivity
and
λ om
is
limiting
molar
conductivity,
C
is
, concentration
in
mole/L
and
A
is
constant
which
depends
on
nature
of
the
electrolyte,
solvent
and
, temperature.
,
, 10. Draw
a
graph
of
molar
conductivity
verses
square
root
of
the
molar
concentration
for
KCl
and
, CH3COOH
mentioning
clearly
each.
, ,
,
,
, 11. How
is
limiting
molar
conductivity
for
a
strong
electrolyte
found
out
by
extrapolation
method?
, Prepare
four
solutions
of
given
strong
electrolyte
of
different
concentrations.
Measure
the
, conductivities
of
each
solutions
using
conductivity
cell
and
calculate
the
molar
conductivities
of
each
, solution.
Plot
a
graph
of
molar
conductivity
verses
square
root
of
the
molar
concentration
for
these
, solutions.
A
straight
line
is
obtained
which
is
to
be
extrapolated
back
so
as
to
touch
the
vertical
axes
, .This
point
of
intersection
on
the
vertical
axes
gives
the
limiting
molar
conductivity.
,
, 12. State
and
illustrate
Faradays
first
law
of
electrolysis.
, The
amount
of
chemical
reaction
which
occurs
at
any
electrode
during
electrolysis
by
a
current
is
, proportional
to
the
quantity
of
electricity
passed
through
the
electrolyte
either
through
its
aqueous
, solution
or
molten
state.
, If
w
is
the
mass
of
the
substance
deposited
and
Q
is
the
current
passed
in
coulombs
,
,
,
w
∝
Q
, But
Q
=
I
t
where
I
is
the
current
strength
in
ampere
and
t
is
time
in
seconds.
,
, 13. Conductivity
of
0.01
M
NaCl
solution
is
0.12
Sm-‐1.
Calculate
its
molar
conductivity.
, , λm =,
,
, , k, 0.12, =, = 1.2 ×10 -2 Sm 2 / mol
, 1000C 1000 × 0.01
Page 5 :
14.
The
molar
conductivity
of
0.1M
nitric
acid
is
630
S
cm2
/mol.
Calculate
its
conductivity.
,
, 1000k, C,
,
, 1000k, 630 =, 0.1, 630 × 0.1, ∴k =, = 0.063 Scm-1, 1000, λm =, ,
, 15. A
solution
of
Ni(NO3)2
is
electrolysed
between
platinum
electrodes
using
a
current
of
5
amperes
for
, 20
minutes.
What
mass
of
nickel
is
deposited
at
the
cathode?
(Mol
mass
of
Ni
=
58.7)
,
Q
=
I
t
,
=
5×20×60
=
6000C
, , Ni 2 + + 2e ⎯⎯⎯⎯⎯→ Ni,
,
, 2 × 96500C, 193000C, 58.7g, For
193000C
of
electricity
mass
of
nickel
obtained
=
58.7g
, For
6000C
of
electricity
, , 6000 × 58.7, = 1.812g
, 193000, ,
, 16. How
long
it
will
take
for
the
deposition
of
0.2g
of
silver
when
silver
nitrate
solution
is
electrolysed
, using
0.5
ampere
of
current
(Mol
mass
of
Ag
=
108)
,
, , Ag + + e - ⎯⎯, → Ag,
, 96500C 108g, For
108g
of
silver
to
be
deposited
current
required
is
96500C.
, For
0.2g
of
Ag
,
, , 0.2 × 96500, = 178.7C = Q
, 108, Q 178.7, t= =, = 357.4 se
, I, 0.5, , But
Q
=
I
t
, , 17.
The
cell
in
which
the
following
reaction
occurs
2Fe3+ ( aq ) + 2I −( aq ) ⎯⎯, → 2Fe2+ ( aq ) + I 2( s )
, Has
Eocell
=
0.236V
at
298K.
Calculate
the
standard
Gibb’s
energy
and
the
equilibrium
constant
for
the
, cell
reaction.
,
,
,
,
n
=
2
,
,
,
, Δ.Go
=
-‐nFEo
,
,
,
=
-‐
2×96500×0.236
,
=
-‐
45548
J
,
Ecell =, , 0.059, log K
, n
Page 6 :
0.059, log K
, 2, 2 × 0.236,
log K =, = 8
, 0.059,
0.236 =, , Taking
the
antilog
K
=
108
,
, 18. Write
the
reaction
taking
place
at
cathode
and
anode
when
aqueous
solution
of
copper
sulphate
is
, electrolysed
using
copper
electrodes.
,
, , oxdn, A t anode Cu( s ) ⎯⎯⎯, → Cu 2+ ( aq ) + 2e −, redn, A t cathode Cu 2+ ( aq ) + 2e − ⎯⎯⎯, → Cu( s ), ,
, , Thus
copper
from
anode
dissolves
and
an
equivalent
amount
of
pure
copper
is
deposited
on
cathode.
, This
technique
is
used
in
electrolytic
refining
of
crude
copper.
,
, 19. Write
the
reaction
taking
place
at
anode
and
cathode
when
molten
NaCl
is
electrolysed.
, When
molten
sodium
chloride
is
electrolysed
using
inert
electrodes
,
, , oxdn, At anode 2Cl − ⎯⎯⎯, → Cl2 + 2e−, redn, At cathode Na + + e− ⎯⎯⎯, → Na, ,
, , Thus
chlorine
gas
is
liberated
at
anode
and
Sodium
metal
is
formed
at
cathode.
,
, 20. Write
the
reaction
taking
place
when
aqueous
solution
of
NaCl
is
electrolysed.
, When
aqueous
solution
of
NaCl
is
electrolysed,
,
, , NaCl ⎯⎯, → Na + + Cl −, +, −, H 2O áà àÜ, àà H + OH, ,
, , The
reaction
taking
place
at
cathode
is
,
H + aq + e− ⎯⎯, →, , 1, H 2( g )
, 2, , The
reaction
taking
place
at
anode
is
,
Cl - aq ⎯⎯, →, , 1, Cl 2 aq + e -
, 2, ,
, 21. What
is
a
primary
battery/cell
?Give
an
example.
, Primary
battery
is
one
in
which
reaction
occurs
only
once
and
cannot
be
recharged.
Eg
Dry
cell
or
, Leclanche
cell
and
Mercury
cell
,
, 22. What
is
a
secondary
battery/cell
?
Give
an
example.
, Secondary
battery
is
one
which
can
be
recharged
by
passing
current
through
it
in
opposite
direction,so
, that
it
can
be
Reused.
, Eg:
Lead
storage
battery
and
Nickel
cadmium
cell.
Page 7 :
23. EoCu
=
+0.34V
and
EoZn
=-‐0.76V.
Daniel
cell
is
obtained
by
coupling
these
two
electrodes.
, (i)
represent
the
cell
symbolically
, (ii)
calculate
the
EMF
of
the
cell
,
, (i)
Daniel
cell
can
be
represented
as
,
Zn/
Zn2+
(aq)
||
Cu2+
(aq)
/Cu
,
, (ii)
EMF
of
Daniel
cell
Eo
cell
=
EoR
-‐
EoL
,
=
EoCu
-‐
EoZn
=
0.34-‐(-‐0.76)
,
=
1.10V
,
, 24. Calculate
the
molar
conductivity
of
a
solution
of
MgCl2
at
infinite
dilution
given
that
the
molar
ionic
, conductivities
of
λo, , ( Mg 2+ ), , = 106.1 Scm 2 mol -1 and λo(, , Cl - ), , = 76.3 Scm 2 mol -1
, , λ o MgCl 2 = λ o Mg 2+ + 2λ o Cl
= 106.1 + 2( 76.3), ,
, , = 258.7 Scm 2 mol -1,
, 25. The
resistance
of
a
conductivity
cell
containing
0.001
M
KCl
solution
at
298K
is
1500Ω .
What
is
the
, cell
constant
if
the
conductivity
of
0.001M
KCl
solution
at
298K
is
0.146×10-‐3
Scm-‐1?
,
, Cell
constant
G*=
Rk
,
=resistance
×
conductivity
,
=0.146×10-‐3
Scm-‐1×1500S-‐1
,
=
0.219
cm-‐1
,
, , Question
carrying
3
or
4
marks
,
, 1. Explain
the
construction
of
Daniel
cell.
Write
the
reaction
taking
place
at
anode
and
cathode
and
the
net
, cell
reaction.
(3
mark)
, To
prepare
Daniel
cell
get
a
zinc
electrode
by
dipping
zinc
rod
in
1M
ZnSO4
solution.
Get
a
copper
, electrode
by
dipping
a
copper
plate
in
1
M
CuSO4
solution.
Couple
these
two
electrodes
using
a
salt
bridge
, to
get
Daniel
cell.
Reactions
taking
place
, ,
, ,
, , +, , A t anode, , oxdn, Zn ⎯⎯⎯, → Zn 2 + 2e −, , At cathode, , redn, Cu 2+ + 2e− ⎯⎯⎯, → Cu, , Net cell reaction Zn( s ) + Cu, , 2+, ( aq ), , ⎯⎯, → Zn, , 2+, ( aq ), , + Cu( s )
Page 8 :
2. With
a
labeled
digram
explain
standar
hydrogen
electrode.
Represent
it
symbolically.
Write
the
reduction
, reaction
at
the
anode.
What
is
its
electrode
potential?
(4
marks)
,
, ,
, It
consists
of
a
platinum
electrode
coated
with
platinum
black.
The
electrode
is
dipped
in
1M
HCl.
Pure
, hydrogen
gas
is
bubbled
through
it
under
a
pressure
of
1
bar.
S.H.E
is
represented
as
,
Pt(s)
|H2
(g)(1bar)
|H+(aq)(1M)
, The
reduction
reaction
taking
place
is
,
H + (aq) + e − ⎯⎯, →, , 1, H 2 ( g )
, 2, , S.H.E
is
assigned
an
electrode
potential
of
0.0
V
at
all
temperatures.
,
, 3. Explain
the
use
of
standard
hydrogen
electrode
in
measuring
the
standard
electrode
potentials
of
copper
, and
zinc
electrode
(4
mark)
, Construct
a
standard
electrode
of
the
given
metal
by
dipping
the
pure
metal
in
1M
solution
of
its
own
ion
, at
25o
C
Couple
this
standard
electrode
with
SHE
using
a
salt
bridge
to
get
galvanic
cell.
Measure
the
emf
, of
the
cell
using
suitable
instrument
like
potentiometer.
,
Eo
=
EoR
–
EoL
, One
of
the
electrodes
of
the
cell
is
SHE
and
its
electrode
potential
is
0.0V.
So
the
electrode
potential
of
the
, given
electrode
will
be
the
emf
of
the
cell
in
magnitude.
If
reduction
takes
place
at
the
given
electrode
its
, Eo
will
be
+ve
but
if
oxidation
takes
place
at
the
given
electrode
is
Eo
will
be
–ve.
, e.g
if
SHE
is
coupled
with
standard
copper
electrode
reduction
takes
place
at
copper
electrode
cell
can
be
, represented
as
,
Pt
(s)
|H2(g.
1bar)|H+(aq1M)||Cu2+(aq.1M)|Cu
, , E o cell = E o Cu 2+ / Cu - E o H + / H
, 2, , 0.34 = E, , o, , Cu 2+ / Cu, , -0, , ∴ E oCu 2+ / Cu = 0.34V
, ,
If
SHE
coupled
with
standard
zinc
electrode
oxidation
takes
place
at
zinc
electrode.
Cell
can
be
, represented
as
Page 9 :
Zn2+ ( aq.1M ) / Zn( s ) ⏐⏐Pt( s )⏐H 2( g .1bar )⏐H + ( aq.1M )
, , E ocell = E o H + / H − E o Zn2+ / Zn
, 2, , 0.76 = 0 − E, , o, , ∴ EZn2+ / Zn = −0.76V
, , Zn2+ / Zn, ,
, 4. How
is
Kohlrausch
law
helpful
in
finding
out
the
limiting
molar
conductivity
of
a
weak
electrolyte?
(3
m)
, Let
us
try
to
calculate
λom
for
a
weak
electrolyte
CH3COOH.
Select
three
strong
electrolytes
whose
λom
can
, be
found
by
extrapolation
method
in
such
a
way
that
if
we
subtract
λom
for
one
electrolyte
from
the
sum
, of
λoms
of
the
remaining
two
electrolyte
λom
for
CH3COOH
can
be
obtained.
The
three
electrolytes
to
be
, selected
are
CH3COONa,
HCl
&
NaCl
,
λo CH, , 3 COOH, , = λo CH3COONa + λo HCl - λo NaCl
, ,
, 5. The
values
of
limiting
molar
conductivities
(λ om)
for
NH4Cl,
NaOH
and
NaCl
are
respectively
149.74;
248.1
, and
126.4
Scm2mol-‐1.
Calculate
the
limiting
molar
conductivity
of
NH4OH
(3M)
,
λo NH, , 4 OH, , = λo NH 4Cl + λo NaOH - λo NaCl
, ,
=
149.74+248.1-‐126.4
,
=
271.44
Scm2
mol-‐1
, 6. Calculate
the
equilibrium
constant
for
the
reaction
at
298K
Cu( s ) + 2 Ag + (aq) ⎯⎯, → Cu 2+( aq ) + 2 Ag( s )
, Given
that
Eo
Ag+/Ag
=
0.80V
and
Eo(Cu2+/Cu)
=
0.34V
, , 0.059, log K c
, n, nE o cell,
∴ log K c =,
, 0.059,
E o cell = E o +, − E o(Cu2+ /Cu )
, ( Ag / Ag ),
E o cell =, ,
=0.80-‐0.34=0.46V
,
log K c =, , 2 × 0.46, = 15.59
, 0.059, ,
Taking
the
antilog
Kc
=3.92×1015
,
, 7. In
Leclanche
cell
(dry
cell)
what
are
anode
and
cathode?
What
is
the
electrolyte
used?
Write
the
reactions
, at
each
electrode.
What
is
the
role
of
zinc
chloride?
,
, It
consists
of
a
zinc
container
as
an
anode.
A
graphite
rod
surrounded
by
a
mixture
of
manganese
dioxide
, and
carbon
powder
is
cathode.
, The
space
between
the
electrodes
is
filled
with
electrolyte
a
moist
paste
of
ammonium
chloride
and
zinc
, chloride
Page 10 :
Reaction
taking
place
, , At anode Zn( s) ⎯⎯, → Zn 2+ + 2e -
, At cathode MnO 2 + NH 4 + + e - ⎯⎯, → MnO( OH) + NH 3
, NH3
produced
in
the
reaction
forms
a
complex
with
Zn2+
to
form
[Zn(NH3)4]2+.
,
, 8. What
are
the
anode
and
cathode
of
lead
acid
battery?
What
is
the
electrolyte?
Write
the
reactions
taking
, place
at
anode
and
cathode
and
the
overall
reaction
during
discharging
of
the
battery.
(3
M)
, It
consists
of
lead
anode
and
a
grid
of
lead
packed
with
lead
dioxide
(PbO2)
as
cathode.
, Electrolyte
is
38%
solution
of
sulphuric
acid.
The
reactions
taking
place
when
the
battery
is
in
use
are
,
, , Anode Pb( s ) + SO4 2− ( aq ) ⎯⎯, → PbSO4( s ) + 2e−, Cathode PbO2 ( s) + SO4 2− ( aq ) + 4 H + ( aq ) + 2e− ⎯⎯, → PbSO4 ( s ) + 2 H 2O, , The
overall
reaction
is
Pb( s ) + PbO2, , ( s), , + 2H 2 SO4, , ( aq ), , ⎯⎯, → 2PbSO4, , ( s), , + 2 H 2O, , (l ), ,
, (l ), ,
, ,
, 9. In
Hydrogen
oxygen
fuel
cell
(i)
Draw
the
schematic
diagram
mentioning
the
anode
and
cathode.
What
is
, the
electrolyte?
Write
the
reaction
taking
place
at
each
electrodes
and
the
net
cell
reaction.
(4M)
, ,
,
, In
this
hydrogen
and
oxygen
gases
are
bubbled
through
porous
carbon
electrodes
into
concentrated
, aqueous
sodium
hydroxide
solution.
Catalyst
like
finely
divided
platinum
or
palladium
is
incorporated
into
, the
electrodes
for
increasing
the
rate
of
electrode
reaction
, Reaction
taking
place
are
, , Cathode, , O 2 ( g)+ 2H 2 O ( l)+ 4e - ⎯⎯, → 4OH -(, , Anode, , 2H 2(, , g) + 4OH (, , aq), , ⎯⎯, → 4H 2 O( l) + 4e -, , Overall
reaction
is
, , 2H 2 ( g)+ O2 ( g) ⎯⎯, → 2H 2O ( l)
,
, , aq)
Page 11 :
10. What
is
corrosion?
During
rusting
of
iron
write
the
anodic
and
cathodic
reactions.
Give
the
composition
, of
rust.
(3M)
, When
a
metal
is
exposed
to
the
atmosphere
it
is
slowly
attacked
by
the
constituents
of
the
environment
, as
a
result
of
which
the
metal
is
slowly
lost
in
the
form
of
its
compound
.
This
is
called
corrosion.
,
, Reaction
taking
place
are
, , At Anode, , 2Fe(, , At Cathode, , O 2 ( g)+ 4H +( aq)+ 4e - ⎯⎯, → 2H 2O(, , s), , ⎯⎯, → 2Fe 2+ + 4e -, ,
, l), , +, , H
are
produced
from
H2CO3
formed
due
to
dissolution
of
carbon
dioxide
from
air
into
water
The
Fe2+
ions
, are
further
oxidised
by
atmospheric
oxygen
to
ferric
ion
which
are
ultimately
converted
to
hydrated
ferric
, oxide
called
rust.
Composition
of
rust
is
(Fe2O3.xH2O).
,
, 11. A
conductivity
cell
when
filled
with
0.01M
KCl
has
a
resistance
of
747.5
ohm
at
25oC.
When
the
same
, cell
was
filled
with
an
aqueous
solution
of
0.05M
CaCl2
solution
the
resistance
was
876
ohm.
Calculate
, (i)
Conductivity
of
the
solution
, (ii
)Molar
conductivity
of
the
solution
(given
conductivity
of
0.01M
KCl
=
0.14114
sm-‐1)
(3M)
,
, Cell
constant
G*
=
Rk
,
=
747.5×0.14114
,
=0.105.5m-‐1
, , cell constant 105.5m -1, =, = 0.1204Sm -1
, R, 876 ohm, k, 0.1204, Molar conductivity λm =, =, = 0.00241sm 2 mol -1
, 1000C 1000 × 0.05, , Conductivity k =, , 12. The
electrical
resistance
of
a
column
of
0.05M
NaOH
solution
of
diameter
1cm
and
length
50cm
is
, 5.55×103
ohm.
Calculate
its
,
(i)
resistivity
,
(ii)
conductivity
,
(iii)
molar
conductivity
,
,
,
,
,
,
,
,
,
(3M)
, Cell
constant
G o =, , l,
, a, , l
=
50
cm
, Diameter
=
1
cm
∴
radius
=
0.5
cm
, Area
of
cross
section
A
=
πr2
=
3.14×(0.5)2
=
0.785
cm3
,
,
G *, , =, , 50, = 63.694 cm -1
, 0.785
Page 12 :
1, 1, =, = 87.135 Ω
, k 1.148 ×10 -2, 1000k, Molarconductivityλm =, C, 1000 ×1.148 ×10 -2, =,
, 0.05, = 229.6 S cm 2 mol -1, , Resistivity ρ =, , 13. Calculate
the
emf
of
the
cell
in
which
the
following
reaction
takes
place.
, , Ni( s ) + 2 Ag + (0.002M ) ⎯⎯, → Ni 2+ (0.160M ) + 2 Ag( s )
,
, Given
that
Eocell
=
1.05V
, , Ecell = E o cell −, , [ Ni 2+ ][ Ag( s ) ]2, 0.059,
, log10, 2, [ Ni( s ) ][ Ag + ]2, , But
[M]
for
any
element
is
taken
as
unity
,
, , E cell = E, = 1.05 =
0.914V
,
,
,
,
,
,
,
,
, , ⎡Ni ⎤⎦, 0.059,
, log10 ⎣, + 2, 2, ⎡⎣ Ag ⎤⎦, 2+, , o, , cell, , 0.059, 0.160,
, log, 2, 2, (0.002 )
