option c nernst equation, voltaic cell and concentration cell
TRANSCRIPT
http://lawrencekok.blogspot.com
Prepared by Lawrence Kok
Tutorial on Voltaic Cell, Nernst Equation and concentration cell.
Types voltaic cell
Conversion electrical energy to chemical energy
Electrochemistry
Electrolytic cellVoltaic cell
NH4CI and ZnCI2
Redox rxn (Oxidation/reduction)Movement electronProduce electricity
Conversion chemical energy to electrical energy
Electrodes – different metal (Half cell) Electrodes – same metal (Half cell)
Daniell cell Alkaline cellDry cell Nickel cadmium cell
Primary cell (Non rechargeable)
MnO2 and KOH
Secondary cell (Rechargeable)
Current – measured Amperes or Coulombs per second 1A = 1 Coulomb charge pass through a point in 1 s = 1C/s1 Coulomb charge (elec) = 6.28 x 10 18 elec passing in 1 s
1 elec/proton carry charge of – 1.6 x 10 -19 C ( very small)6.28 x 10 18 elec carry charge of - 1 C
Electric current
Flow electric charges (elec, -ve)From High to low electric potential Potential Diff – measure with ammeter
ondelectron
ondCoulombA
sec.1.1028.6
sec111
18
Current Electric Current – moving charges in solid wire or solution
Flow of charges
---
Solid/WireSolution/Electrolyte
Electron move in random No current flow cause
No potential difference
Electrons & Protons
--
++
1A = 6.28 x 1018 e 1 s
Potential Difference across wireElectron move in one direction
Current flow
+ve ions -ve ions(cations) (anions)
Potential Diff applied/Battery
ItQ t = Time/ s
Find amt charges pass through if Current is 2.ooA, time is 15 min
ItQ
Current flow
Q = Amt Charges/ C I = Current/ A
CQ 1800601500.2
Electric Potential
CJVolt 11
-Measured in Volt with Voltmeter- 1 V = 1 Joule energy released when 1 Coulomb charge pass through 1 point- 1 V = 1 J/C
V = Potential DiffI = CurrentR = Resistance
Potential diff bet 2 points is 1 V ↓1 J energy released when 1 C charge passes through
Voltmeter across1Volt
1 V
+ -
1 Ω 2 Ω
Charges (-ve) flow down
ARVI
RIV
236
VVRIV212
-+-
+
VVRIV422
Total current
Potential Diff(PD) vs CurrentPD = Water Pressure
PD = 1.5V – 1.5J energy released 1C charge flow downPD – cause charge flow = CURRENT
Potential Diff(PD) vs Current
1.5V = 1.5J/CA
DElectric potential/PD/Voltage = Electric Pressure = VoltElectric Current = Charge flow = Amp
Electric Potential Energy = Work done to bring a charge to a point = JouleVoltage NOT same as energy, Voltage = energy/charge
Battery lift charges, Q to higher potentialPotential Energy bet 2 terminals in battery stored as chemical energy
2A 2A
Potential Diff/VoltagePotential Diff/Voltage
EMF vs PD
V = Potential DiffI = CurrentR = Resistance
Max potential diff bet two
electrodes of battery source. + -
1 Ω 2 Ω
ARVI
RIV
236
VVRIV212
VV
RIV422
Total current
Current flow Circuit complete
Circuit complete↓
Current flow↓
Internal resistance(battery - 1Ω)
↓Terminal PD = 8V
(Voltage drop)
Potential Diff/Voltage in Volt
Symbol for EMF = E / ℰ
No Current flow in circuit
EMF (Electromotive Force) VoltBattery = EMF = 9V
9 Volt
).(9 currentnoVEMFVIRV
EMF Internal resistance Ir
Place voltmeter across – EMF= 9V
No current flow.
ArR
EI
rRIEIrIREMFE
199
)18(9
)(
)()(
VVRIV881
VVRIV111
EMF = 8V+1V
8 Volt
1 Volt
EMF (6V) = 2V + 4V
4 Volt2 Volt
Charges passing through wire
Current flow Circuit complete
Internal resistanceCollision bet + ve ions with elec
(drift velocity elec)
- +
Eθ value DO NOT depend surface area of metal electrode.E cell = Energy per unit charge. (Joule)/CE cell- 10v = 10J energy released by 1C of charge = 100J energy released by 10C of charge Eθ – intensive property– independent of amt – Ratio energy/chargeIncreasing surface area metal will NOT increase E cell
Eθ Zn/Cu = 1.10V
Surface area - 10 cm2 Total charge- 100C leave electrodeE cell = 1.1V = 1.1 J energy for 1 C (charges leaving) 1C release 1.1 J energy100 C release 110 J energyVoltmeter measure energy for 1C – 110J/100C – 1.1VE cell no change
Current – measured in Amp or Coulomb per s1A = 1 Coulomb charge pass through a point in 1 s = 1C/s1 Coulomb charge (elec) = 6.28 x 10 18 elec passing in 1 s
1 electron/proton carry charge of – 1.6 x 10 -19 C ( very small)6.28 x 10 18 electron carry charge of - 1 C
ondelectron
ondCoulombA
sec.1.1028.6
sec111
18
Surface area increase ↑
Total Energy increase ↑
Total Charge increase ↑ Current increase ↑
BUT E cell remain SAMEE cell = (Energy/charge)t
QI
tIQ
Q up ↑ – I up ↑
100C flow110J released
VEcell
Ecell
eChEnergyEcell
10.1100110arg
Surface area - 100 cm2 Total charge 1000C leave electrodeE cell = 1.1V = 1.1 J energy for 1 C (charges leaving) 1 C release 1.1J energy1000 C release 1100 J energyVoltmeter measure energy for 1C – 1100J/1000C – 1.1VE cell no change
VEcell
Ecell
eChEnergyEcell
10.110001100arg
Eθ Zn/Cu = 1.10V
1000C flow1100J released
tQI
tQI
Surface area exposed 10 cm2
Surface area exposed 100 cm2
∆G θ = -nFE θ cell
Relationship bet ∆G and Kc
cellnFEG
Relationship betEnergetics and Equilibrium
cKRTG ln STHG Enthalpy change
Entropy change
Equilibrium constant
Gibbs free energy change
HG
Relationship bet ∆G, Kc and E cell
cellnFEG STHG cKRTG ln
cK
Relationship betEnergetics and Cell Potential
G cellE
Gibbs free energy change
Cell potential
F = Faraday constant (96 500 Cmol-1)
n = number electron
Relationship bet ∆G, Kc and Ecell
ΔGθ Kc Eθ/V Extent of rxn
> 0 < 1 < 0 No ReactionNon spontaneous
ΔGθ = 0 Kc = 1
0 EquilibriumMix
reactant/product
< 0 > 1 > 0 Reaction completeSpontaneous
ΔGθ Kc Eq mixture
ΔGθ = + 200
9 x 10-36 Reactants
ΔGθ = + 10 2 x 1-2 Mixture
ΔGθ = 0 Kc = 1 Equilibrium
ΔGθ = - 10 5 x 101 Mixture
ΔGθ = - 200 1 x 1035 Products
shift to left (reactant)
shift to right (products)
cellE
G
cK∆G
θ = -RT ln
K c
KnFRTE cell ln
ΔGθ ln K Kc Eq mixture
ΔGθ -ve < 0
Positive ( + )
Kc > 1
Product(Right)
ΔGθ +ve > 0
Negative
( - )
Kc < 1
Reactant(left)
ΔGθ = 0 0 Kc = 1
Equilibrium
E cell/Voltage – depend on nature of material
QnFRTEE ln
T = Temp in KQ = Rxn Quotient
E0 = std (1M)n = # e transfer
F = Faraday constant (96 500C mol -1 )
R = Gas constant (8.31)
cKRTQRTG lnln
KRTG
KRTQRTGo
c
ln
lnln
When ratio conc, Q = 1,
all in std conc = 1M
Non std condition
01ln1
RTQ
QnFRTEE ln
QRTGG o lnNon std condition
onFEG nFEG
QRTnFEnFE ln
Nernst equation
Work or Free energy to do work depend on quantity material and surface area
E cell depend
Nature of electrodeType of metal used Conc of ion Temp of sol
Eθ Q T
Current/I depend
Surface area of contact
Salt bridge conc Size of cation/anion
Resistance high ↑ – current low ↓E cell depend
Surface area of contact Salt bridge conc
Size of cation/anion
cellnFEG
Gibbs free energy changedo do WORK
n = number electron
F = Faraday constant (96 500 Cmol-1)
Cell potential
Increasing surface area → increase charge Q and I current - Work increase
Current – depend on quantity and surface area
Zn ↔ Zn2+ + 2e Eθ = +0.76Cu2+ + 2e ↔ Cu Eθ = +0.34Zn + Cu2+ → Zn 2+ + Cu Eθ = +1.10V
Zn half cell (-ve)Oxidation
Cu half cell (+ve)Reduction
Anode Cathode
Zn(s) | Zn2+(aq) || Cu2+
(aq) | Cu (s)
Anode Cathode
Half Cell Half Cell(Oxidation) (Reduction)
Salt Bridge Flow electrons
Zn/Cu Cell - 1M std condition
-e -e
Eθcell = Eθ
(cathode) – Eθ (anode)
Eθcell = +0.34 – (-0.76) = +1.10V
Zn 2+ + 2e ↔ Zn (anode) Eθ = -0.76VCu2+ + 2e ↔ Cu (cathode) Eθ = +0.34V
Eθcell = Eθ
(cathode) – Eθ(anode)
Zn 2+ + 2e ↔ Zn Eθ = -0.76VCu2+ + 2e ↔ Cu Eθ = +0.34V
Oxidized sp ↔ Reduced sp Eθ/VLi+ + e- ↔ Li -3.04K+ + e- ↔ K -2.93Ca2+ + 2e- ↔ Ca -2.87Na+ + e- ↔ Na -2.71Mg 2+ + 2e- ↔ Mg -2.37Al3+ + 3e- ↔ AI -1.66Mn2+ + 2e- ↔ Mn -1.19H2O + e- ↔ 1/2H2 + OH- -0.83Zn2+ + 2e- ↔ Zn - 0.76Fe2+ + 2e- ↔ Fe -0.45Ni2+ + 2e- ↔ Ni -0.26Sn2+ + 2e- ↔ Sn -0.14Pb2+ + 2e- ↔ Pb -0.13H+ + e- ↔ 1/2H2 0.00Cu2+ + e- ↔ Cu+ +0.15SO4
2- + 4H+ + 2e- ↔ H2SO3 +0.17Cu2+ + 2e- ↔ Cu + 0.341/2O2 + H2O +2e- ↔ 2OH- +0.40
+
+1.10 V
Eθ Zn/Cu = 1.10V
Cu2+
----
Zn Cu++++
cellnFEG
E cell with ∆G
F = Faraday constant (96 500 Cmol-1)
n = number electron
cellnFEG
kJJG
G
212212300
10.1965002
Std electrode potential - std reduction potential
STD CONDITION
Zn/Cu half cell Cell diagram
QnFRTEE ln
Ratio conc, Q = 1, all in std conc = 1M, T =
298K
VE
E
10.1
1ln965002298314.810.1
Zn ↔ Zn2+ + 2e Eθ = +0.762Ag++2e ↔ 2Ag Eθ = +0.80Zn + Ag+ → Zn 2+ + Ag Eθ = +1.56V
Zn half cell (-ve)Oxidation
Ag half cell (+ve)Reduction
Anode Cathode
Zn(s) | Zn2+(aq) || Ag+
(aq) | Ag (s)
Anode Cathode
Half Cell Half Cell(Oxidation) (Reduction)
Salt Bridge Flow electrons
-e -e
Eθcell = Eθ
(cathode) – Eθ (anode)
Eθcell = +0.80 – (-0.76) = +1.56V
Zn 2+ + 2e ↔ Zn (anode) Eθ = -0.76VAg + + e ↔ Ag(cathode) Eθ = +0.80V
Eθcell = Eθ
(cathode) – Eθ(anode)
Zn 2+ + 2e ↔ Zn Eθ = -0.76VAg+ + e ↔ Ag Eθ = +0.80V
Oxidized sp ↔ Reduced sp Eθ/VLi+ + e- ↔ Li -3.04K+ + e- ↔ K -2.93Ca2+ + 2e- ↔ Ca -2.87Na+ + e- ↔ Na -2.71Mg 2+ + 2e- ↔ Mg -2.37Al3+ + 3e- ↔ AI -1.66Mn2+ + 2e- ↔ Mn -1.19H2O + e- ↔ 1/2H2 + OH- -0.83Zn2+ + 2e- ↔ Zn - 0.76Fe2+ + 2e- ↔ Fe -0.45Ni2+ + 2e- ↔ Ni -0.26Sn2+ + 2e- ↔ Sn -0.14Pb2+ + 2e- ↔ Pb -0.13H+ + e- ↔ 1/2H2 0.00Cu2+ + e- ↔ Cu+ +0.15SO4
2- + 4H+ + 2e- ↔ H2SO3 +0.17Cu2+ + 2e- ↔ Cu +0.341/2O2 + H2O +2e- ↔ 2OH- +0.40Cu+ + e- ↔ Cu +0.521/2I2 + e- ↔ I- +0.54Fe3+ + e- ↔ Fe2+ +0.77Ag+ + e- ↔ Ag + 0.801/2Br2 + e- ↔ Br- +1.07
+
+1.56 V
Ag
Eθ Zn/Ag = +1.56V
Ag+
----
++++
Zn
E cell with ∆G
cellnFEG
n = number electron F = Faraday constant (96 500 Cmol-1)
cellnFEG
kJJG
G
301301000
56.1965002
Cell diagram Zn/Ag half cells
Ratio conc, Q = 1, all in std conc = 1M, T =
298K
Zn/Ag Cell - 1M std condition
QnFRTEE ln
VE
E
56.1
1ln965002298314.856.1
STD CONDITION
Zn half cell (-ve)Oxidation
Cu half cell (+ve)Reduction
Zn/Cu Cell
-e -e
Zn 2+ + 2e ↔ Zn Eθ = -0.76VCu2+ + 2e ↔ Cu Eθ = +0.34V
Zn ↔ Zn2+ + 2e Eθ = +0.76VCu2+ + 2e ↔ Cu Eθ = +0.34VZn + Cu2+ → Zn 2+ + Cu Eθ = +1.10V
Oxidized sp ↔ Reduced sp Eθ/VLi+ + e- ↔ Li -3.04K+ + e- ↔ K -2.93Ca2+ + 2e- ↔ Ca -2.87Na+ + e- ↔ Na -2.71Mg 2+ + 2e- ↔ Mg -2.37Al3+ + 3e- ↔ AI -1.66Mn2+ + 2e- ↔ Mn -1.19H2O + e- ↔ 1/2H2 + OH- -0.83Zn2+ + 2e- ↔ Zn - 0.76Fe2+ + 2e- ↔ Fe -0.45Ni2+ + 2e- ↔ Ni -0.26Sn2+ + 2e- ↔ Sn -0.14Pb2+ + 2e- ↔ Pb -0.13H+ + e- ↔ 1/2H2 0.00Cu2+ + e- ↔ Cu+ +0.15SO4
2- + 4H+ + 2e- ↔ H2SO3 + H2O +0.17Cu2+ + 2e- ↔ Cu + 0.341/2O2 + H2O +2e- ↔ 2OH- +0.40Cu+ + e- ↔ Cu +0.521/2I2 + e- ↔ I- +0.54
+1.10 V
Cu2+
----
Zn Cu++++
QnFRTEE ln 1M 0.1M
Zn2+
10]1.0[]1[
][][
2
2
c
c
QMM
CuZnQ
0.1 M 1 M
Using Nernst Eqn
E0 = Std condition (1M) – 1.10VR = Gas constant (8.31)n = # e transfer (2 e)F = Faraday constant (96500C mol -1 )
VEE
E
07.103.010.1
)10ln()965002()29831.8(10.1
Non std 0.1M
E cell decrease ↓ [Cu2+] decrease ↓↓
Le Chatelier’s principleCu2+ + 2e ↔ Cu
↓[Cu2+] decrease ↓
↓Shift to left ←
↓
E cell → less ↓ → Cu2+ less able ↓ to receive e- [Cu2+] ↓ E cell < Eθ
1.07 < 1.10
Zn/Cu half cell Zn +Cu2+→Zn2++Cu
NON STD CONDITION
Zn half cell (-ve)Oxidation
Cu half cell (+ve)Reduction
Zn/Cu Cell
-e -e
Zn 2+ + 2e ↔ Zn Eθ = -0.76VCu2+ + 2e ↔ Cu Eθ = +0.34V
Zn ↔ Zn2+ + 2e Eθ = +0.76VCu2+ + 2e ↔ Cu Eθ = +0.34VZn + Cu2+ → Zn 2+ + Cu Eθ = +1.10V
Oxidized sp ↔ Reduced sp Eθ/VLi+ + e- ↔ Li -3.04K+ + e- ↔ K -2.93Ca2+ + 2e- ↔ Ca -2.87Na+ + e- ↔ Na -2.71Mg 2+ + 2e- ↔ Mg -2.37Al3+ + 3e- ↔ AI -1.66Mn2+ + 2e- ↔ Mn -1.19H2O + e- ↔ 1/2H2 + OH- -0.83Zn2+ + 2e- ↔ Zn - 0.76Fe2+ + 2e- ↔ Fe -0.45Ni2+ + 2e- ↔ Ni -0.26Sn2+ + 2e- ↔ Sn -0.14Pb2+ + 2e- ↔ Pb -0.13H+ + e- ↔ 1/2H2 0.00Cu2+ + e- ↔ Cu+ +0.15SO4
2- + 4H+ + 2e- ↔ H2SO3 + H2O +0.17Cu2+ + 2e- ↔ Cu + 0.341/2O2 + H2O +2e- ↔ 2OH- +0.40Cu+ + e- ↔ Cu +0.521/2I2 + e- ↔ I- +0.54
+1.10 V
Cu2+
----
Zn Cu++++
QnFRTEE ln 1M 10M
Zn2+
1.0]10[]1[
][][
2
2
c
c
QMM
CuZnQ
10 M 1 M
Using Nernst Eqn
E0 =Std condition (1M) – 1.10VR = Gas constant (8.31)n = # e transfer (2 e)F = Faraday constant (96500C mol -1 )
VEE
E
13.103.010.1
)1.0ln()965002()29831.8(10.1
Non std 0.1M
E cell increase ↑ [Cu2+] increase ↑↓
Le Chatelier’s principleCu2+ + 2e ↔ Cu
↓[Cu2+] increase ↑
↓Shift to right →
↓E cell → more ↑→ Cu2+ more able receive e-
[Cu2+] ↑ E cell > Eθ
1.13 > 1.10
Zn/Cu half cell Zn +Cu2+→Zn2++Cu
NON STD CONDITION
Zn half cell (-ve)Oxidation
Cu half cell (+ve)Reduction
Zn/Cu Cell
-e -e
Zn 2+ + 2e ↔ Zn Eθ = -0.76VCu2+ + 2e ↔ Cu Eθ = +0.34V
Zn ↔ Zn2+ + 2e Eθ = +0.76VCu2+ + 2e ↔ Cu Eθ = +0.34VZn + Cu2+ → Zn 2+ + Cu Eθ = +1.10V
Oxidized sp ↔ Reduced sp Eθ/VLi+ + e- ↔ Li -3.04K+ + e- ↔ K -2.93Ca2+ + 2e- ↔ Ca -2.87Na+ + e- ↔ Na -2.71Mg 2+ + 2e- ↔ Mg -2.37Al3+ + 3e- ↔ AI -1.66Mn2+ + 2e- ↔ Mn -1.19H2O + e- ↔ 1/2H2 + OH- -0.83Zn2+ + 2e- ↔ Zn - 0.76Fe2+ + 2e- ↔ Fe -0.45Ni2+ + 2e- ↔ Ni -0.26Sn2+ + 2e- ↔ Sn -0.14Pb2+ + 2e- ↔ Pb -0.13H+ + e- ↔ 1/2H2 0.00Cu2+ + e- ↔ Cu+ +0.15SO4
2- + 4H+ + 2e- ↔ H2SO3 + H2O +0.17Cu2+ + 2e- ↔ Cu + 0.341/2O2 + H2O +2e- ↔ 2OH- +0.40Cu+ + e- ↔ Cu +0.521/2I2 + e- ↔ I- +0.54
+1.10 V
Cu2+
----
Zn Cu++++
QnFRTEE ln 0.1M 1M
Zn2+
1.0]1[]1.0[
][][
2
2
c
c
QMM
CuZnQ
1 M 0.1 M
Using Nernst Eqn
E0 = Std condition (1M) – 1.10VR = Gas constant (8.31)n = # e transfer (2 e)F = Faraday constant (96500C mol -1 )
VEE
E
13.103.010.1
)1.0ln()965002()29831.8(10.1
Non std 0.1M
E cell increase ↑ [Zn2+] decrease ↓↓
Le Chatelier’s principleZn2+ + 2e ↔ Zn
↓[Zn2+] decrease ↓
↓Shift to left ←
↓E cell → more ↑→ Zn more able lose elec
[Zn2+] ↓ E cell > Eθ
1.13 > 1.10
Zn/Cu half cell Zn + Cu2+→ Zn2+ + Cu
NON STD CONDITION
Cu half cell (-ve)Oxidation
Cu half cell (+ve)Reduction
-e
Cu ↔ Cu 2+ + 2e Eθ = - 0.34VCu2+ + 2e ↔ Cu Eθ = +0.34V
Cu ↔ Cu2+ + 2e Eθ = - 0.34VCu2+ + 2e ↔ Cu Eθ = +0.34VCu + Cu2+ → Cu2+ + Cu Eθ = 0V
Oxidized sp ↔ Reduced sp Eθ/VLi+ + e- ↔ Li -3.04K+ + e- ↔ K -2.93Ca2+ + 2e- ↔ Ca -2.87Na+ + e- ↔ Na -2.71Mg 2+ + 2e- ↔ Mg -2.37Al3+ + 3e- ↔ AI -1.66Mn2+ + 2e- ↔ Mn -1.19H2O + e- ↔ 1/2H2 + OH- -0.83
Zn2+ + 2e- ↔ Zn -0.76Fe2+ + 2e- ↔ Fe -0.45Ni2+ + 2e- ↔ Ni -0.26Sn2+ + 2e- ↔ Sn -0.14Pb2+ + 2e- ↔ Pb -0.13H+ + e- ↔ 1/2H2 0.00Cu2+ + e- ↔ Cu+ +0.15SO4
2- + 4H+ + 2e- ↔ H2SO3 + H2O +0.17Cu2+ + 2e- ↔ Cu + 0.341/2O2 + H2O +2e- ↔ 2OH- +0.40
Cu2+
Zn Cu++++
QnFRTEE ln
0.1M
01.0]1.0[]001.0[
][][
2
2
c
cathode
anodec
QCuCu
Q
0.1 M 0.001 M
Using Nernst Eqn
E0 = Std condition (1M) – 1.10VR = Gas constant (8.31)n = # e transfer (2 e)F = Faraday constant (96500C mol -1 )
VEE
E
0285.00285.00
)01.0ln()965002()29831.8(0
Cu2+/Cu half cell Cu + Cu2+ → Cu2+ + Cu -e
Cu2+
0.001M
Cu (s) Cu2+(aq) (0.001M) Cu2+
(aq) (0.1M)Cu(s)
----
Concentration cellElectrode same - diff conc
Oxi cell – anode – lower concRed cell – cathode – higher conc
cathode anode
Cu
Conc cell made of Zn/Zn2+
Conc Zn2+ - 0.11M and 0.22M. Find voltage.Zn (s) Zn2+
(aq) (0.11M) Zn2+(aq) (0.22M)Zn(s)
Zn + Zn2+ → Zn2+ + Zn
cathode anode
0.22M 0.11 M
5.0]22.0[]11.0[
][][
2
2
c
cathode
anodec
QZnZn
Q QnFRTEE ln
VE
E
0089.0
)5.0ln()965002()29831.8(0
Fe half cell (-ve)Oxidation
Fe half cell (+ve)Reduction
-e
Fe ↔ Fe 2+ + 2e Eθ = + 0.45VFe2+ + 2e ↔ Fe Eθ = - 0.45V
Fe ↔ Fe2+ + 2e Eθ = + 0.45VFe2+ + 2e ↔ Fe Eθ = - 0.45 VFe + Fe2+ → Fe2+ +Fe Eθ = 0V
Oxidized sp ↔ Reduced sp Eθ/VLi+ + e- ↔ Li -3.04K+ + e- ↔ K -2.93Ca2+ + 2e- ↔ Ca -2.87Na+ + e- ↔ Na -2.71Mg 2+ + 2e- ↔ Mg -2.37Al3+ + 3e- ↔ AI -1.66Mn2+ + 2e- ↔ Mn -1.19H2O + e- ↔ 1/2H2 + OH- -0.83
Zn2+ + 2e- ↔ Zn -0.76Fe2+ + 2e- ↔ Fe -0.45Ni2+ + 2e- ↔ Ni -0.26Sn2+ + 2e- ↔ Sn -0.14Pb2+ + 2e- ↔ Pb -0.13H+ + e- ↔ 1/2H2 0.00Cu2+ + e- ↔ Cu+ +0.15SO4
2- + 4H+ + 2e- ↔ H2SO3 + H2O +0.17
Fe2+
Zn Fe++++
QnFRTEE ln
0.1M
1.0]1.0[]01.0[
][][
2
2
c
cathode
anodec
QFeFe
Q
0.1 M 0.01 M
Using Nernst Eqn
E0 = Std condition (1M) – 1.10VR = Gas constant (8.31)n = # e transfer (2 e)F = Faraday constant (96500C mol -1 )
VEE
E
029.0029.00
)1.0ln()965002()29831.8(0
Fe2+/Fe half cell Fe + Fe2+ → Fe2++ Fe -e
Fe2+
0.01M
Fe(s)Fe2+(aq) (0.01M) Fe2+
(aq) (0.1M)Fe(s)
----
Concentration cellElectrode same - in diff concOxi cell – anode – lower conc
Red cell – cathode – higher conc
cathode anode
Fe
Find cell potentialMn (s) Mn2+
(aq) (0.1M) Pb2+(aq) (0.0001M)Pb(s)
Mn + Pb2+ → Mn2+ + Pb
0.0001M 0.1 M
cathode anode 001.0]0001.0[]1.0[
][][
2
2
c
cathode
anodec
QPbMn
Q QnFRTEE ln
VE
E
96.0
)001.0ln()965002()29831.8(05.1
Acknowledgements
Thanks to source of pictures and video used in this presentation
Thanks to Creative Commons for excellent contribution on licenseshttp://creativecommons.org/licenses/http://spmchemistry.onlinetuition.com.my/2013/10/electrolytic-cell.htmlhttp://www.chemguide.co.uk/physical/redoxeqia/introduction.htmlhttp://educationia.tk/reduction-potential-tablehttp://2012books.lardbucket.org/books/principles-of-general-chemistry-v1.0/s23-electrochemistry.html
Prepared by Lawrence Kok
Check out more video tutorials from my site and hope you enjoy this tutorialhttp://lawrencekok.blogspot.com