IB Chemistry on Standard Reduction Potential, Standard Hydrogen Electrode and Electrochemical Series

http://lawrencekok.blogspot.com
Prepared by
Lawrence Kok
Tutorial on Standard Electrode Potential, Standard
Reduction Potential and Electrochemical Series.

Potential Diff bet Zn/Zn2+
Electrode potential Zn/Zn2+
= -ve
-
Electrode Potential
Redox Equilibrium
Zn2+
Zn → Zn 2+
+ 2e
(Oxidation)
Zn 2+
+ 2e → Zn
(Reduction)
Zn 2+
+ 2e ↔ Zn
(At equilibrium)
Metal Zn placed in its sol Zn2+
ion
Equilibrium bet Zn/Zn2+
Zn metal reactive lose e form Zn2+
Equilibrium shift to right ←
Potential Diff form bet Zn/Zn2+
Potential Diff
Electrode potential = -ve
Zn2+
Zn2+
Zn
Zn2+
Zn
Zn2+
Zn2+
Zn2+
Zn 2+
+ 2e ↔ Zn
Equi shift to ←
-
--
Zn
-
-
-
-
+
+
+
+
+ +
+ +
+
Voltage of Zn/Zn2+
can’t be measured.
Abs electrode potential can’t measured.
Only Diff in electrode potential can be measured.
Cannot measure
Abs Potential
Metal Cu placed in its sol Cu2+
ion
Equilibrium bet Cu/Cu2+
Cu2+
ion gain -2e form Cu
Equilibrium shift to left ←
Potential Diff form bet Cu/Cu2+
Potential Diff
Electrode potential = +ve
Cu
Cu2+
Cu2+
Cu2+
Cu2+
Cu → Cu2+
+ 2e
(Oxidation)
Cu2+
+ 2e → Cu
(Reduction)
Cu2+
+ 2e ↔ Cu
(At equilibrium)
Cu
-e
-e
-e
Cu2+
Cu2+
Cu2+
Cu2+
+ 2e ↔ Cu
Equi shift to →
Zn Half Cell
+
+
+
Cu
+
+
+
-
--
-
--- ----
--
Potential Diff bet Cu/Cu2+
Electrode potential Cu/Cu2+
= +ve
Cannot measure
Abs Potential
Voltage of Cu/Cu2+
can’t be measured.
Abs electrode potential can’t measured.
Only Diff in electrode potential can be measured.
PDF version
Online version
Click here chem database
(std electrode potential)
Click here interactive ECS Click here pdf version ECS
Cu Half Cell

Potential Diff Cu/Cu2+
Electrode potential
Cu/Cu2+
= +ve
Potential Diff Zn/Zn2+
Electrode potential
Zn/Zn2+
= -ve
Zn2+
Zn → Zn 2+
+ 2e
(Oxidation)
Zn 2+
+ 2e → Zn
(Reduction)
Zn 2+
+ 2e ↔ Zn
(At equilibrium)
Zn2+
Zn2+
Zn
Zn2+
Zn
Zn2+
Zn2+
Zn2+
Zn 2+
+ 2e ↔ Zn
Equi shift to ←
-
-
-
Zn
-
--
-
+
++
+
+ +
+
+
+
Can’t measure
Abs Potential
Cu
Cu2+
Cu2+
Cu2+
Cu2+
Cu → Cu2+
+ 2e
(Oxidation)
Cu2+
+ 2e → Cu
(Reduction)
Cu2+
+ 2e ↔ Cu
(At equilibrium)
Cu
-e
-e
-e
Cu2+
Cu2+
Cu2+
Cu2+
+ 2e ↔ Cu
Equi shift to →
Zn Half Cell
+
+
+
Cu
+
+
+
-
Cu Half Cell
Zn/Cu Voltaic Cell
External circuit – flow of electrons
Complete circuit
-
--
--
-
-
----
-- -
Connect 2 Half Cell with wire/ salt bridge
Zn half cell (-ve)
Oxidation
Cu half cell (+ve)
Reduction
Salt Bridge – flow of ions
Complete the circuit
Cu2+
+ 2e → CuZn → Zn 2+
+ 2e
Zn + Cu2+
→ Zn2+
+ Cu
Anode Cathode
Maintain electrical
neutrality
Salt bridge – saturated KNO3
Zn2+
increase ↑
NO3
-
flow in to balance excess Zn2+
Cu2+ decrease ↓, excess –ve ion ↑
K+
flow in to balance loss of Cu2+
Zn Cu
--
-
-
Zn2+
Zn2+
Zn2+
Excess of Zn2+
ion
+
+
++
-
-
-
-
---
-
-
-
-
-
Excess of –ve ion
+
+
+
+
++
+
Without Salt Bridge
-+
+
+
+
With Salt Bridge
(electron unable to flow due to ESF)
NO3
-
NO3
-
NO3
-
NO3
-
+
+
+ K
+
K
+
K
+
-
-
-
K+
flow in to balance
excess of – ion
NO3
-
flow in to balance
excess of + ion
2 Half Cell to make a Voltaic Cell
-e -e
-
-
-
-
+
+
+
+

Electrode potential
Cu/Cu2+
= +ve
Electrode potential
Zn/Zn2+
= -ve
Zn2+
Zn → Zn 2+
+ 2e
(Oxidation)
Zn 2+
+ 2e → Zn
(Reduction)
Zn 2+
+ 2e ↔ Zn
(At equilibrium)
Zn2+
Zn2+
Zn
Zn2+
Zn
Zn2+
Zn2+
Zn2+
Zn 2+
+ 2e ↔ Zn
Equi shift to ←
-
-
-
Zn
-
--
-
+
++
+
+ +
+
+
+
Can’t measure
Abs Potential
Cu
Cu2+
Cu2+
Cu2+
Cu2+
Cu → Cu2+
+ 2e
(Oxidation)
Cu2+
+ 2e → Cu
(Reduction)
Cu2+
+ 2e ↔ Cu
(At equilibrium)
Cu
-e
-e
-e
Cu2+
Cu2+
Cu2+
Cu2+
+ 2e ↔ Cu
Equi shift to →
+
+
+
Cu
+
+
+
-
Complete circuit
-
--
--
-
-
----
-- -
Zn half cell (-ve)
Oxidation
Cu half cell (+ve)
Reduction
Voltmeter – High resistance
(No current flow) Salt Bridge – flow of ions
Cu2+
+ 2e → CuZn → Zn 2+
+ 2e
1.10Volt
Potential diff can be measured.
Voltmeter across – EMF
1.10 Volt
Zn + Cu2+
→ Zn2+
+ Cu
Anode Cathode
Zn(s) | Zn2+
(aq) || Cu2+
(aq)| Cu (s)
Cell diagram
Anode Cathode
Half Cell Half Cell
(Oxidation) (Reduction)
Phase boundarySalt Bridge Flow
electrons
Maintain electrical
neutrality
Zn2+
increase ↑
NO3
-
Cu2+ decrease ↓
K+
flow in to balance loss of Cu2+
Zn/Cu Voltaic Cell 2 Half Cell to make a Voltaic Cell
Zn Half Cell Cu Half Cell
-e -e
-
-
-
-
+
+
+
+

Potential Diff Ag/Ag2+
Electrode potential
Ag/Ag2+
= +ve
Electrode potential
Zn/Zn2+
= -ve
Zn2+
Zn → Zn 2+
+ 2e
(Oxidation)
Zn 2+
+ 2e → Zn
(Reduction)
Zn 2+
+ 2e ↔ Zn
(At equilibrium)
Zn2+
Zn2+
Zn
Zn2+
Zn
Zn2+
Zn2+
Zn2+
Zn 2+
+ 2e ↔ Zn
Equi shift to ←
-
-
-
Zn
-
--
-
+
++
+
+ +
+
+
+
Can’t measure
Abs Potential
Ag
Ag+
Ag+
Ag+
Ag+
Ag → Ag+
+ e
(Oxidation)
Ag+
+ e → Ag
(Reduction)
Ag+
+ e ↔ Ag
(At equilibrium)
Ag
-e
-e
-e
Ag+
Ag+
Ag+
Ag+
+ e ↔ Ag
Equi shift to →
+
+
+
Ag
+
+
+
-
Complete circuit
-
--
--
-
-
----
-- -
Zn half cell (-ve)
Oxidation
Ag half cell (+ve)
Reduction
Ag+
+ e → AgZn → Zn 2+
+ 2e
1.56Volt
1.56 Volt
Zn + 2Ag+
→ Zn2+
+ 2Ag
Anode Cathode
Zn(s) | Zn2+
(aq) || Ag+
(aq)| Ag (s)
Cell diagram
Anode Cathode
Half Cell Half Cell
electrons
Maintain electrical
neutrality
Zn2+
increase ↑
NO3
-
Ag+ decrease ↓
K+
flow in to balance loss of Ag+
Zn/Ag Voltaic Cell 2 Half Cell to make a Voltaic Cell
Zn Half Cell Ag Half Cell
Ag
Ag+
-e -e
-
-
-
-
+
+
+
+

Potential Diff Ag/Ag2+
Electrode potential
Ag/Ag2+
= +ve
Electrode potential
Cu/Cu2+
= -ve
Cu2+
Cu → Cu 2+
+ 2e
(Oxidation)
Cu 2+
+ 2e → Cu
(Reduction)
Cu 2+
+ 2e ↔ Cu
(At equilibrium)
Cu2+
Cu2+
Cu
Cu2+
Cu
Cu2+
Cu2+
Cu2+
Cu 2+
+ 2e ↔ Cu
Equi shift to ←
-
-
-
Cu
-
--
-
+
++
+
+ +
+
+
+
Can’t measure
Abs Potential
Ag
Ag+
Ag+
Ag+
Ag+
Ag → Ag+
+ e
(Oxidation)
Ag+
+ e → Ag
(Reduction)
Ag+
+ e ↔ Ag
(At equilibrium)
Ag
-e
-e
-e
Ag+
Ag+
Ag+
Ag+
+ e ↔ Ag
Equi shift to →
+
+
+
Ag
+
+
+
-
Complete circuit
-
--
--
-
-
----
-- -
Cu half cell (-ve)
Oxidation
Ag half cell (+ve)
Reduction
Ag+
+ e Ag→Cu → Cu 2+
+ 2e
0.46Volt
0.46 Volt
Cu + 2Ag+
→ Cu2+
+ 2Ag
Anode Cathode
Cu(s) | Cu2+
(aq) || Ag+
(aq)| Ag (s)
Cell diagram
Anode Cathode
Half Cell Half Cell
electrons
Maintain electrical
neutrality
Cu2+
increase ↑
NO3
-
flow in to balance excess Cu2+
Ag+ decrease ↓
K+
flow in to balance loss of Ag+
Cu/Ag Voltaic Cell 2 Half Cell to make a Voltaic Cell
Cu Half Cell Ag Half Cell
Ag
Ag+
Cu
Cu2+
-e -e
-
-
-
-
+
+
+
+

Standard Electrode Potential
Standard Hydrogen Electrode (SHE)
Platinum coat with Platinum oxide/black
– increase surface area for adsorption H2
- catalyze equilibrium bet H2 /H+
- H2 ↔ 2H+
+ 2e-
Eθ
Standard Reference electrode
All Cell Potential are measured against
• Conc ( 1M)
• Pressure (1 atm)
• Temp (298K)
• Platinum- inert electrode
(sys without metal)
Standard
condition
H2 at 1 atm
Platinum
H2 gas
Pt wire
Platinum
2H+
+ 2e ↔ H2
Eθ
= 0V
Types of Half Cells
Metal/ Ion (M/M+
)
Gas/ Ion (M/M-
)
Ion/ Ion (Fe3+
/Fe2+
)
• Pure Zn metal
• Conc (1M Zn2+
)
• Temp (298K)
Condition Std Zn/Zn2+
Condition Std CI2/CI-
• CI2 gas
• Platinum electrode
• Conc (1M CI-
)
• Temp (298K)
• Conc (1M Fe3+
/Fe2+
)
• Temp (298K)
Condition Std Fe3+
/ Fe2+
Zn2+
Zn
Fe3+
/Fe2+
CI-
Condition for Standard
C
A
N
T
M
E
A
S
U
R
E
A
B
S
P
O
T
E
N
T
I
A
L
1
2
3
How to measure
electrode
potential ?
Pt
1M H+
Measure
Difference?

Std Hydrogen Electrode (SHE)
Eθ
= 0V
Types of Half Cells
Metal/ Ion (M/M+)
Gas/ Ion (M/M+
)
Ion/ Ion (Fe3+
/Fe2+
)
• Pure Zn metal
• Conc (1M Zn2+
)
• Temp (298K)
Condition Std Zn/Zn2+
Condition Std CI2/CI-
• CI2 gas
• Conc (1M CI-
)
• Temp (298K)
• Conc (1M Fe3+
/Fe2+
)
• Temp (298K)
Condition Std Fe3+
/ Fe2+
Zn2+
Zn
Fe3+
/Fe2+
1
2
3
Connect to SHE
Connect to SHE
Connect to SHE
Eθ
= 0V
Eθ
= 0V
Eθ
= -0.76V
Standard electrode potential Zn/Zn2+
= -0.76V
Eθ
cell = -0.76V
Eθ
= +0.77V
Eθ
= +1.35V
Standard electrode potential Fe3+
/Fe2+
= +0.77V
Eθ
cell = +0.77V
Standard electrode potential CI2 /CI-
= +1.35V
Eθ
cell = +1.35V
Eθ
= -0.76V
Eθ
= +0.77V
Eθ
= +1.35V
2 Half Cell with SHE as reference electrode
CI-
Pt
+
+
+
Pt

Std Electrode Potential diff systems
Eθ
= 0V
Eθ
= 0V
Eθ
= 0V
Eθ
= -0.76V
Standard electrode potential Zn/Zn2+
= -0.76V
Eθ
cell = -0.76V
Eθ
= +0.77V
Eθ
= +1.35V
Standard electrode potential Fe3+
/Fe2+
= +0.77V
Eθ
cell = +0.77V
Standard electrode potential CI2 /CI-
= +1.35V
Eθ
cell = +1.35V
Eθ
= -0.76V
Eθ
= +0.77V
Eθ
= +1.35V
STANDARD Reduction potential – Hydrogen as std
Oxidized sp ↔ Reduced sp Eθ
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
H2O + e- 1/2H↔ 2 -0.83
Zn2+
+ 2e- Zn↔ -0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ -0.26
Sn2+
+ 2e- Sn↔ -0.14
Pb2+
+ 2e- Pb↔ -0.13
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2SO3 + H2O +0.17
Cu2+
+ 2e- ↔ Cu +0.34
1/2O2 + H2O +2e- ↔ 2OH-
+0.40
Cu+
+ e- ↔ Cu +0.52
1/2I2 + e- ↔ I-
+0.54
Fe3+
+ e- ↔ Fe2+
+0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+ 7H2O +1.33
1/2CI2 + e- ↔ CI-
+1.35
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
1/2F2 + e- ↔ F +2.87
-ve
reduction
potential
+ve
reduction
potential
Click here std analogy video
Click here std analogy
PDF version
Compared to
H2 as std
Eθ
cell/Cell Potential = EMF in volt
EMF prod when half cell connect to SHE at std condition
Std electrode potential written as std reduction potential

Zn half cell (-ve)
Oxidation
H2 half cell (+ve)
Reduction
Anode Cathode
Zn(s) | Zn2+
(aq) || H+
(aq) , H2(g) | Pt (s)
Cell diagram
Anode Cathode
Half Cell Half Cell
Salt Bridge Flow
electrons
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Eθ
cell = 0.00 – ( Eθ
Zn )
0.76 = 0.00 - Eθ
Zn
Eθ
Zn = -0.76V
Zn2+
+ 2e Zn E↔ θ
= ?
2H+
+ 2e ↔ H2 Eθ
= 0.00V
Std electrode potential as std reduction potential
Find Eθ
cell (use formula)
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
H2O + e- 1/2H↔ 2 + OH-
-0.83
Zn2+
+ 2e- Zn↔ ????
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ -0.26
Sn2+
+ 2e- Sn↔ -0.14
Pb2+
+ 2e- Pb↔ -0.13
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2SO3 + H2O +0.17
Cu2+
+ 2e- ↔ Cu +0.34
1/2O2 + H2O +2e- ↔ 2OH-
+0.40
Cu+
+ e- ↔ Cu +0.52
1/2I2 + e- ↔ I-
+0.54
Fe3+
+ e- ↔ Fe2+
+ 0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+ 7H2O +1.33
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
1/2F2 + e- ↔ F +2.87
-0.76V
+ve/high electrode potential is cathode (+)
-ve/ low electrode potential is anode (-)
Electrons flow from anode (- ) to cathode (+ )
Eθ
Zn/H2 = 0.76V
Zn/H2
Zn
Zn2+
H+
Pt
H2
-
-
- +
-e
Zn/H2 Cell Determine Eθ
cell Zn/Zn2+
Eθ
value DO NOT depend on stoichiometric coefficient
(Independent of stoichiometric eqn)

H2 half cell (-ve)
Oxidation
Fe3+/2+
half cell (+ve)
Reduction
Anode Cathode
Pt(s) | H2, H+
(aq) || Fe3+
Fe2+
| Pt (s)
Cell diagram
Anode Cathode
Half Cell Half Cell
Salt Bridge Flow
electrons
Find Eθ
cell (use formula)
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
H2O + e- 1/2H↔ 2 + OH-
-0.83
Zn2+
+ 2e- Zn↔ -0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ -0.26
Sn2+
+ 2e- Sn↔ -0.14
Pb2+
+ 2e- Pb↔ -0.13
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2SO3 + H2O +0.17
Cu2+
+ 2e- ↔ Cu +0.34
1/2O2 + H2O +2e- ↔ 2OH-
+0.40
Cu+
+ e- ↔ Cu +0.52
1/2I2 + e- ↔ I-
+0.54
Fe3+
+ e- ↔ Fe2+
?????
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+ 7H2O +1.33
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
1/2F2 + e- ↔ F +2.87
+0.77V
Eθ
H2 /Fe3+
= 0.77V
Pt
Fe3+
H+
Pt
H2
+
+
+--
-e
H2 /Fe3+
,Fe2+
Cell
H2 /Fe3+
,Fe2+
2H+
+ 2e ↔ H2 Eθ
= 0.00V
Fe3+
+ e Fe↔ 2+
Eθ
= ????
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Eθ
cell = Eθ
Fe3+
– (-0.00)
0.77 = Eθ
Fe3+
Determine Eθ
cell Fe 3+
/Fe2+
Eθ

H2 half cell (-ve)
Oxidation
CI2 half cell (+ve)
Reduction
Anode
Pt(s) | H2, H+
(aq) || CI2 ,CI-
| Pt (s)
Cell diagram
Anode Cathode
Half Cell Half Cell
Salt Bridge Flow
electrons
Find Eθ
cell (use formula)
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
H2O + e- 1/2H↔ 2 + OH-
-0.83
Zn2+
+ 2e- Zn↔ -0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ -0.26
Sn2+
+ 2e- Sn↔ -0.14
Pb2+
+ 2e- Pb↔ -0.13
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2SO3 + H2O +0.17
Cu2+
+ 2e- ↔ Cu +0.34
1/2O2 + H2O +2e- ↔ 2OH-
+0.40
Cu+
+ e- ↔ Cu +0.52
1/2I2 + e- ↔ I-
+0.54
Fe3+
+ e- ↔ Fe2+
+ 0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+ 7H2O +1.33
1/2CI2 + e- ↔ CI-
?????
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
1/2F2 + e- ↔ F +2.87
+1.35V
Eθ
H2 /CI2 = 1.35V
H+
Pt
H2 --
-e
H2 /CI2 Cell
2H+
+ 2e ↔ H2 Eθ
= 0.00V
CI + e CI↔ -
Eθ
= ?????
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Eθ
cell = Eθ
CI2 – (-0.00)
1.35 = Eθ
CI2
H2 /CI2 Cell
+
Pt
CI - CI2
Determine Eθ
cell H2 /CI2
Eθ

Zn half cell (-ve)
Oxidation
Cu half cell (+ve)
Reduction
Anode Cathode
Zn(s) | Zn2+
(aq) || Cu2+
(aq) | Cu (s)
Cell diagram
Anode Cathode
Half Cell Half Cell
Salt Bridge Flow
electrons
Zn/Cu Voltaic Cell
-e -e
Zn/Cu half cells
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Eθ
cell = +0.34 – (-0.76) = +1.10V
Zn 2+
+ 2e Zn (anode) E↔ θ
= -0.76V
Cu2+
+ 2e Cu (cathode) E↔ θ
= +0.34V
Find Eθ
cell (use reduction potential)Find Eθ
cell (use formula)
Zn + Cu2+
Zn→ 2+
+ Cu Eθ
= ?????
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Zn 2+
+ 2e Zn E↔ θ
= -0.76V
Cu2+
+ 2e Cu E↔ θ
= +0.34V
Zn Zn↔ 2+
+ 2e Eθ
= +0.76
Cu2+
+ 2e Cu E↔ θ
= +0.34
Zn + Cu2+
Zn→ 2+
+ Cu Eθ
= +1.10V
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
H2O + e- 1/2H↔ 2 + OH-
-0.83
Zn2+
+ 2e- Zn↔ - 0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ -0.26
Sn2+
+ 2e- Sn↔ -0.14
Pb2+
+ 2e- Pb↔ -0.13
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2SO3 + H2O +0.17
Cu2+
+ 2e- ↔ Cu + 0.34
1/2O2 + H2O +2e- ↔ 2OH-
+0.40
Cu+
+ e- ↔ Cu +0.52
1/2I2 + e- ↔ I-
+0.54
Fe3+
+ e- ↔ Fe2+
+0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+ 7H2O +1.33
1/2CI2 + e- ↔ CI-
+1.35
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
1/2F2 + e- ↔ F +2.87
+
+1.10 V
Eθ
Zn/Cu = 1.10V
Cu2+
-
-
-
-
Zn Cu
+
+
+
+
Eθ

Zn half cell (-ve)
Oxidation
Ag half cell (+ve)
Reduction
Anode Cathode
Zn(s) | Zn2+
(aq) || Ag+
(aq) | Ag (s)
Cell diagram
Anode Cathode
Half Cell Half Cell
Salt Bridge Flow
electrons
Zn/Ag Voltaic Cell
-e -e
Zn/Ag half cells
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Eθ
cell = +0.80 – (-0.76) = +1.56V
Zn 2+
= -0.76V
Ag+
+ e Ag(cathode) E↔ θ
= +0.80V
Find Eθ
cell (use formula)
Zn + Ag+
Zn→ 2+
+ Ag Eθ
= ?????
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Zn 2+
+ 2e Zn E↔ θ
= -0.76V
Ag+
+ e Ag E↔ θ
= +0.80V
Zn Zn↔ 2+
+ 2e Eθ
= +0.76
2Ag+
+2e 2Ag E↔ θ
= +0.80
Zn + Ag+
Zn→ 2+
+ Ag Eθ
= +1.56V
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
H2O + e- 1/2H↔ 2 + OH-
-0.83
Zn2+
+ 2e- Zn↔ - 0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ -0.26
Sn2+
+ 2e- Sn↔ -0.14
Pb2+
+ 2e- Pb↔ -0.13
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2SO3 + H2O +0.17
Cu2+
+ 2e- ↔ Cu +0.34
1/2O2 + H2O +2e- ↔ 2OH-
+0.40
Cu+
+ e- ↔ Cu +0.52
1/2I2 + e- ↔ I-
+0.54
Fe3+
+ e- ↔ Fe2+
+0.77
Ag+
+ e- ↔ Ag + 0.80
1/2Br2 + e- ↔ Br-
+1.07
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+ 7H2O +1.33
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
1/2F2 + e- ↔ F +2.87
+
+1.56 V
Ag
Eθ
Zn/Ag = 1.56V
Ag+
-
-
-
-
+
+
+
+
Zn
Eθ

Cu half cell (-ve)
Oxidation
Ag half cell (+ve)
Reduction
Anode Cathode
Cu(s) | Cu2+
(aq) || Ag+
(aq) | Ag (s)
Cell diagram
Anode Cathode
Half Cell Half Cell
Salt Bridge Flow
electrons
Cu/Ag Voltaic Cell
-e -e
Cu/Ag half cells
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Eθ
cell = +0.80 – (+0.34) = +0.46V
Cu 2+
+ 2e Cu (anode) E↔ θ
= +0.34V
Ag+
= +0.80V
Find Eθ
cell (use formula)
Cu + 2Ag+
Cu→ 2+
+ 2Ag Eθ
= ?????
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Cu 2+
+ 2e Cu E↔ θ
= +0.34V
Ag+
+ e Ag E↔ θ
= +0.80V
Cu Cu↔ 2+
+ 2e Eθ
= -0.34
2Ag+
+ 2e 2Ag E↔ θ
= +0.80
Cu + 2Ag+
Cu→ 2+
+ 2Ag Eθ
= +0.46V
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
H2O + e- 1/2H↔ 2 + OH-
-0.83
Zn2+
+ 2e- Zn↔ -0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ -0.26
Sn2+
+ 2e- Sn↔ -0.14
Pb2+
+ 2e- Pb↔ -0.13
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2SO3 + H2O +0.17
Cu2+
+ 2e- ↔ Cu +0.34
1/2O2 + H2O +2e- ↔ 2OH-
+0.40
Cu+
+ e- ↔ Cu +0.52
1/2I2 + e- ↔ I-
+0.54
Fe3+
+ e- ↔ Fe2+
+0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+ 7H2O +1.33
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
1/2F2 + e- ↔ F +2.87
+
+0.46V
AgCu
Cu2+
Half cell- high electrode potential is cathode (+)
Half cell - low electrode potential is anode (-)
Eθ
Cu/Ag = 0.46V
Ag+
-
-
-
-
+
+
+
+
Eθ

Mn half cell (-ve)
Oxidation
Ni half cell (+ve)
Reduction
Anode Cathode
Mn(s) | Mn2+
(aq) || Ni2+
(aq) | Ni (s)
Cell diagram
Anode Cathode
Half Cell Half Cell
Salt Bridge Flow
electrons
Mn/Ni Voltaic Cell
-e -e
Mn/Ni half cells
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Eθ
cell = -0.26 – (-1.19) = +0.93V
Mn 2+
+ 2e Mn (anode) E↔ θ
= -1.19V
Ni2+
+ 2e Ni (cathode) E↔ θ
= -0.26V
Find Eθ
cell (use formula)
Mn + Ni2+
Mn→ 2+
+ Ni Eθ
= ?????
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Mn 2+
+ 2e Mn E↔ θ
= -1.19V
Ni2+
+ 2e Ni E↔ θ
= -0.26V
Mn Mn↔ 2+
+ 2e Eθ
= +1.19
Ni2+
+ 2e Ni E↔ θ
= -0.26
Mn + Ni2+
Mn→ 2+
+ Ni Eθ
= +0.93V
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
H2O + e- 1/2H↔ 2 + OH-
-0.83
Zn2+
+ 2e- Zn↔ -0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ - 0.26
Sn2+
+ 2e- Sn↔ -0.14
Pb2+
+ 2e- Pb↔ -0.13
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2SO3 + H2O +0.17
Cu2+
+ 2e- ↔ Cu +0.34
1/2O2 + H2O +2e- ↔ 2OH-
+0.40
Cu+
+ e- ↔ Cu +0.52
1/2I2 + e- ↔ I-
+0.54
Fe3+
+ e- ↔ Fe2+
+0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+ 7H2O +1.33
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
1/2F2 + e- ↔ F +2.87
+
+0.93 V
Eθ
Mn/Ni = 0.93V
Ni2+
-
-
-
-
NiMn
+
+
+
+Mn2+
Eθ

Fe half cell (-ve)
Oxidation
MnO4- half cell (+ve)
Reduction
Anode Cathode
Fe(s) | Fe2+
(aq) || MnO4
-
,H+
, Mn2+
| Pt (s)
Cell diagram
Anode Cathode
Half Cell Half Cell
Salt Bridge Flow
electrons
Fe/MnO4
-
Voltaic Cell
-e -e
Fe/MnO4
-
half cells
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Eθ
cell = +1.51 – (-0.45) = +1.96V
Fe2+
+ 2e Fe E↔ θ
= -0.45V
MnO4
-
+ 5e ↔ Mn2+
+ 4H2O Eθ
= +1.51V
Find Eθ
cell (use formula)
5Fe + 2MnO4
-
+ 16H+
5Fe→ 2+
+2Mn2+
+ 8H2O Eθ
= ?
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Fe 2+
+ 2e Fe E↔ θ
= -0.45V
MnO4
-
+ 5e ↔ Mn2+
+ 4H2O Eθ
= +1.51V
Fe Fe↔ 2+
+ 2e Eθ
= +0.45
MnO4
-
+5e Mn↔ 2+
+ 4H2O Eθ
= +1.51
Fe + MnO4
-
Mn→ 2+
+ Fe2+
Eθ
= +1.96V
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
H2O + e- 1/2H↔ 2 + OH-
-0.83
Zn2+
+ 2e- Zn↔ -0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ -0.26
Sn2+
+ 2e- Sn↔ -0.14
Pb2+
+ 2e- Pb↔ -0.13
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2SO3 + H2O +0.17
Cu2+
+ 2e- ↔ Cu +0.34
1/2O2 + H2O +2e- ↔ 2OH-
+0.40
Cu+
+ e- ↔ Cu +0.52
1/2I2 + e- ↔ I-
+0.54
Fe3+
+ e- ↔ Fe2+
+0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+ 7H2O +1.33
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
1/2F2 + e- ↔ F +2.87
+
+1.96V
PtFe
Fe2+
Eθ
Fe/MnO4
-
= 1.96V
MnO4
-
Mn2+
Using platinum electrode
-
-
-
-
+
+
+
+
Eθ

Zn half cell (-ve)
Oxidation
Fe3+/2+
half cell (+ve)
Reduction
Anode Cathode
Zn(s) | Zn2+
(aq) || Fe3+
, Fe2+
(aq) | Pt (s)
Cell diagram
Anode Cathode
Half Cell Half Cell
Salt Bridge Flow
electrons
Zn/Fe3+
,Fe2+
Cell
-e -e
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Eθ
cell = +0.77 – (-0.76) = +1.53V
Zn2+
+ 2e Zn E↔ θ
= -0.76V
Fe3+
+ e ↔ Fe2+
Eθ
= +0.77V
Find Eθ
cell (use formula)
Zn + 2Fe3+
Zn→ 2+
+2Fe2+
Eθ
= ?
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Zn 2+
+ 2e Zn E↔ θ
= -0.76V
Fe3+
+ e ↔ Fe2+
Eθ
= +0.77V
Zn Zn↔ 2+
+ 2e Eθ
= +0.76
2Fe3
+2e 2Fe↔ 2+
Eθ
= +0.77
Zn + 2Fe3+
Zn→ 2+
+ 2Fe2+
Eθ
= +1.53V
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
H2O + e- 1/2H↔ 2 + OH-
-0.83
Zn2+
+ 2e- Zn↔ -0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ -0.26
Sn2+
+ 2e- Sn↔ -0.14
Pb2+
+ 2e- Pb↔ -0.13
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2SO3 + H2O +0.17
Cu2+
+ 2e- ↔ Cu +0.34
1/2O2 + H2O +2e- ↔ 2OH-
+0.40
Cu+
+ e- ↔ Cu +0.52
1/2I2 + e- ↔ I-
+0.54
Fe3+
+ e- ↔ Fe2+
+ 0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+ 7H2O +1.33
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
1/2F2 + e- ↔ F +2.87
+
+1.53V
PtZn
Zn2+
Eθ
Zn/Fe3+
= 1.53V
Fe3+-
Fe2+
Zn/Fe3+
,Fe2+
-
-
-
-
+
+
+
+
Eθ

Zn half cell (-ve)
Oxidation
I2 half cell (+ve)
Reduction
Anode Cathode
Zn(s) | Zn2+
(aq) || I2 , I-
(aq) | Pt (s)
Cell diagram
Anode Cathode
Half Cell Half Cell
Salt Bridge Flow
electrons
Zn/I2 , I-
Cell
-e -e
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Eθ
cell = +0.54 – (-0.76) = +1.30V
Zn2+
+ 2e Zn E↔ θ
= -0.76V
I2 + 2e ↔ 2I-
Eθ
= +0.54V
Find Eθ
cell (use formula)
Zn + I2 Zn→ 2+
+2I-
Eθ
= ?
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Zn Zn↔ 2+
+ 2e Eθ
= +0.76
I2 + 2e 2I↔ -
Eθ
= +0.54
Zn + I2 Zn→ 2+
+ 2I-
Eθ
= +1.30V
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
H2O + e- 1/2H↔ 2 + OH-
-0.83
Zn2+
+ 2e- Zn↔ -0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ -0.26
Sn2+
+ 2e- Sn↔ -0.14
Pb2+
+ 2e- Pb↔ -0.13
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2SO3 + H2O +0.17
Cu2+
+ 2e- ↔ Cu +0.34
1/2O2 + H2O +2e- ↔ 2OH-
+0.40
Cu+
+ e- ↔ Cu +0.52
1/2I2 + e- ↔ I-
+0.54
Fe3+
+ e- ↔ Fe2+
+ 0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+ 7H2O +1.33
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
1/2F2 + e- ↔ F +2.87
+
+1.30V
PtZn
Zn2+
Eθ
Zn/I2 = 1.30V
I--
I2
-
-
-
-
+
+
+
+
Zn/I2 , I-
Zn2+
+ 2e Zn E↔ θ
= -0.76V
I2 + 2e ↔ 2I-
Eθ
= +0.54V
Eθ

Zn half cell (-ve)
Oxidation
H2 half cell (+ve)
Reduction
Anode Cathode
Zn(s) | Zn2+
(aq) || H+
(aq) , H2(g) | Pt (s)
Cell diagram
Anode Cathode
Half Cell Half Cell
Salt Bridge Flow
electrons
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Eθ
cell = 0.00 – (-0.76) = +0.76V
Zn2+
+ 2e Zn E↔ θ
= -0.76V
2H+
+ 2e ↔ H2 Eθ
= 0.00V
Find Eθ
cell (use formula)
Zn + 2H+
Zn→ 2+
+ H2 Eθ
= ?
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Zn 2+
+ 2e Zn E↔ θ
= -0.76V
2H+
+ 2e ↔ H2 Eθ
= 0.00V
Zn Zn↔ 2+
+ 2e Eθ
= +0.76
2H+
+2e H↔ 2 Eθ
= 0.00
Zn + 2H+
Zn→ 2+
+ H2 Eθ
= +0.76V
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
H2O + e- 1/2H↔ 2 + OH-
-0.83
Zn2+
+ 2e- Zn↔ -0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ -0.26
Sn2+
+ 2e- Sn↔ -0.14
Pb2+
+ 2e- Pb↔ -0.13
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2SO3 + H2O +0.17
Cu2+
+ 2e- ↔ Cu +0.34
1/2O2 + H2O +2e- ↔ 2OH-
+0.40
Cu+
+ e- ↔ Cu +0.52
1/2I2 + e- ↔ I-
+0.54
Fe3+
+ e- ↔ Fe2+
+ 0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+ 7H2O +1.33
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
1/2F2 + e- ↔ F +2.87
+
+0.76V
Eθ
Zn/H2 = 0.76V
Using platinum electrode/H2
Zn/H2
Zn
Zn2+
H+
Pt
H2
-
-
- +
-e
Zn/H2 Cell
Eθ

H2 half cell (-ve)
Oxidation
Ag half cell (+ve)
Reduction
Anode Cathode
Pt(s) | H2, H+
(aq) || Ag+
(aq) | Ag (s)
Cell diagram
Anode Cathode
Half Cell Half Cell
Salt Bridge Flow
electrons
H2/Ag Cell
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Eθ
cell = +0.80 – (-0.00) = +0.80V
2H+
+ 2e ↔ H2 Eθ
= 0.00V
Ag+
+ e Ag E↔ θ
= +0.80V
Find Eθ
cell (use formula)
H2 + 2Ag+
2H→ +
+ 2Ag Eθ
= ?
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
H2 2H↔ +
+ 2e Eθ
= +0.00
2Ag+
+2e 2Ag E↔ θ
= +0.80
H2 + 2Ag+
2H→ +
+ 2Ag Eθ
= +0.80V
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
H2O + e- 1/2H↔ 2 + OH-
-0.83
Zn2+
+ 2e- Zn↔ -0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ -0.26
Sn2+
+ 2e- Sn↔ -0.14
Pb2+
+ 2e- Pb↔ -0.13
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2SO3 + H2O +0.17
Cu2+
+ 2e- ↔ Cu +0.34
1/2O2 + H2O +2e- ↔ 2OH-
+0.40
Cu+
+ e- ↔ Cu +0.52
1/2I2 + e- ↔ I-
+0.54
Fe3+
+ e- ↔ Fe2+
+ 0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+ 7H2O +1.33
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
1/2F2 + e- ↔ F +2.87
+
+0.80V
Eθ
H2 /Ag = 0.80V
H2/Ag
Ag
Ag+
H+
Pt
H2
2H+
+ 2e ↔ H2 Eθ
= 0.00V
Ag+
+ e Ag E↔ θ
= +0.80V
+
+
+--
-e
Eθ

H2 half cell (-ve)
Oxidation
Fe3+/2+
half cell (+ve)
Reduction
Anode Cathode
Pt(s) | H2, H+
(aq) || Fe3+
Fe2+
| Pt (s)
Cell diagram
Anode Cathode
Half Cell Half Cell
Salt Bridge Flow
electrons
Find Eθ
cell (use formula)
H2 + 2Fe3+
2H→ +
+ 2Fe 2+
Eθ
= ?
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
H2 2H↔ +
+ 2e Eθ
= +0.00
2Fe3+
+2e 2Fe↔ 2+
Eθ
= +0.77
H2 + 2Fe3+
2H→ +
+ 2Fe2+
Eθ
= +0.77V
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
H2O + e- 1/2H↔ 2 + OH-
-0.83
Zn2+
+ 2e- Zn↔ -0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ -0.26
Sn2+
+ 2e- Sn↔ -0.14
Pb2+
+ 2e- Pb↔ -0.13
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2SO3 + H2O +0.17
Cu2+
+ 2e- ↔ Cu +0.34
1/2O2 + H2O +2e- ↔ 2OH-
+0.40
Cu+
+ e- ↔ Cu +0.52
1/2I2 + e- ↔ I-
+0.54
Fe3+
+ e- ↔ Fe2+
+ 0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+ 7H2O +1.33
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
1/2F2 + e- ↔ F +2.87
+
+0.77V
Eθ
H2 /Fe3+
= 0.77V
Pt
Fe3+
H+
Pt
H2
+
+
+--
-e
H2 /Fe3+
,Fe2+
Cell
H2 /Fe3+
,Fe2+
2H+
+ 2e ↔ H2 Eθ
= 0.00V
Fe3+
+ e Fe↔ 2+
Eθ
= +0.77V
2H+
+ 2e ↔ H2 Eθ
= 0.00V
Fe3+
+ e Fe↔ 2+
Eθ
= +0.77V
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Eθ
cell = +0.77– (-0.00) = +0.77V
Eθ

H2 half cell (-ve)
Oxidation
CI2 half cell (+ve)
Reduction
Anode Cathode
Pt(s) | H2, H+
(aq) || CI2 ,CI-
| Pt (s)
Cell diagram
Anode Cathode
Half Cell Half Cell
Salt Bridge Flow
electrons
Find Eθ
cell (use formula)
CI2 + H2 2CI→ -
+ 2H+
Eθ
= ?
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
H2 2H↔ +
+ 2e Eθ
= +0.00
CI2 +2e 2CI↔ -
Eθ
= +1.35
H2 + CI2 2H→ +
+ 2CI-
Eθ
= +1.35V
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
H2O + e- 1/2H↔ 2 + OH-
-0.83
Zn2+
+ 2e- Zn↔ -0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ -0.26
Sn2+
+ 2e- Sn↔ -0.14
Pb2+
+ 2e- Pb↔ -0.13
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2SO3 + H2O +0.17
Cu2+
+ 2e- ↔ Cu +0.34
1/2O2 + H2O +2e- ↔ 2OH-
+0.40
Cu+
+ e- ↔ Cu +0.52
1/2I2 + e- ↔ I-
+0.54
Fe3+
+ e- ↔ Fe2+
+ 0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+ 7H2O +1.33
1/2CI2 + e- ↔ CI-
+1.35
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+1.51
1/2F2 + e- ↔ F +2.87
+
+1.35V
Eθ
H2 /CI2 = 1.35V
Eθ
H+
Pt
H2 --
-e
H2 /CI2 Cell
2H+
+ 2e ↔ H2 Eθ
= 0.00V
CI + e CI↔ -
Eθ
= +1.35V
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Eθ
cell = +1.35 – (-0.00) = +1.35V
H2 /CI2 Cell
2H+
+ 2e ↔ H2 Eθ
= 0.00V
CI + e CI↔ -
Eθ
= +1.35V
+
Pt
CI - CI2

STANDARD Reduction potential – H2 as std
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
H2O + e- H↔ 2+OH-
-0.83
Zn2+
+ 2e- Zn↔ -0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ -0.26
Sn2+
+ 2e- Sn↔ -0.14
Pb2+
+ 2e- Pb↔ -0.13
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2SO3 +0.17
Cu2+
+ 2e- ↔ Cu +0.34
1/2O2 + H2O +2e- ↔ 2OH-
+0.40
Cu+
+ e- ↔ Cu +0.52
1/2I2 + e- ↔ I-
+0.54
Fe3+
+ e- ↔ Fe2+
+0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+7H2O +1.33
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
1/2F2 + e- ↔ F-
+2.87
-ve
reduction
potential
+ve
reduction
potential
Compared to
H2 as std
Eθ
EMF when half cell connect to SHE std condition
Std potential written as std reduction potential
TOP right
• High ↑ tendency lose e
• Li Li→ +
+ e
• Eθ
Li = +3.04V
• STRONG reducing Agent
•Oxi favourable
(Eθ
=+ve)
TOP right
• Li Li→ +
+ e
• Eθ
Li = +3.04V
•Oxi favourable
(Eθ
=+ve)
STRONG
Reducing Agent
WEAK
Reducing Agent
BOTTOM right
• Low ↓ tendency lose e
• F -
1/2F→ 2 + e
• Eθ
F2 = - 2.87V
• WEAK reducing Agent
•Oxi NOT favourable (Eθ
=-ve)
BOTTOM right
• F -
1/2F→ 2 + e
• Eθ
F2 = - 2.87V
• WEAK reducing Agent
•Oxi NOT favourable (Eθ
=-ve)
WEAK
Oxidizing Agent
STRONG
Oxidizing Agent
TOP left
• Low ↓ tendency gain e
• Li+
+ e Li→
• Eθ
Li= - 3.04V
• WEAK oxidizing Agent
• Red NOT favourable
(Eθ
=-ve)
TOP left
• Li+
+ e Li→
• Eθ
Li= - 3.04V
• WEAK oxidizing Agent
• Red NOT favourable
(Eθ
=-ve)
BOTTOM left
• High ↑ tendency gain e
• F2 + 2e 2F→ -
• Eθ
F2= +2.87V
• STRONG oxidizing Agent
•Red favourable (Eθ
=+ve)
BOTTOM left
• F2 + 2e 2F→ -
• Eθ
F2= +2.87V
=+ve)
О
О
О
О

STANDARD Reduction potential – H2 as std
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
H2O + e- H↔ 2+OH-
-0.83
Zn2+
+ 2e- Zn↔ -0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ -0.26
Sn2+
+ 2e- Sn↔ -0.14
Pb2+
+ 2e- Pb↔ -0.13
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2SO3 +0.17
Cu2+
+ 2e- ↔ Cu +0.34
1/2O2 + H2O +2e- ↔ 2OH-
+0.40
Cu+
+ e- ↔ Cu +0.52
1/2I2 + e- ↔ I-
+0.54
Fe3+
+ e- ↔ Fe2+
+0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+7H2O +1.33
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
1/2F2 + e- ↔ F -
+2.87
Eθ
TOP right
• Li Li→ +
+ e
• Eθ
Li = +3.04V
•Oxi favourable (Eθ
=+ve)
TOP right
• Li Li→ +
+ e
• Eθ
Li = +3.04V
=+ve)
STRONG
Reducing Agent
STRONG
Oxidizing Agent
BOTTOM left
• F2 + 2e 2F→ -
• Eθ
F2= +2.87V
•Red favourable (Eθ =+ve)
BOTTOM left
• F2 + 2e 2F→ -
• Eθ
F2= +2.87V
•Red favourable (Eθ =+ve)
Li Li→ +
+ e Eθ
Li = +3.04VLi Li→ +
+ e Eθ
Li = +3.04V
1/2F2 + e F→ - Eθ
F2 = + 2.87V1/2F2 + e F→ -
Eθ
F2 = + 2.87V
Click here ebook notes
Click here interactive ECS

/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
H2O + e- H↔ 2+OH-
-0.83
Zn2+
+ 2e- Zn↔ -0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ -0.26
Sn2+
+ 2e- Sn↔ -0.14
Pb2+
+ 2e- Pb↔ -0.13
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2SO3 + H2O +0.17
Cu2+
+ 2e- ↔ Cu +0.34
1/2O2 + H2O +2e- ↔ 2OH-
+0.40
Cu+
+ e- ↔ Cu +0.52
1/2I2 + e- ↔ I-
+0.54
Fe3+
+ e- ↔ Fe2+
+0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+7H2O +1.33
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
1/2F2 + e- ↔ F -
+2.87
-ve
potential
+ve
potential
Uses of Standard Electrode Potential (SEP) Data1
TOP left
• Li+
+ e Li→
• Eθ
Li= - 3.04V
• Red NOT favourable (Eθ
=-ve)
TOP left
• Li+
+ e Li→
• Eθ
Li= - 3.04V
=-ve)
WEAK
Oxidizing
Agent
STRONG
Oxidizing
Agent
О
TOP right
• Li Li→ +
+ e
• Eθ
Li = +3.04V
=+ve)
TOP right
• Li Li→ +
+ e
• Eθ
Li = +3.04V
=+ve)
STRONG
Reducing
Agent
О
WEAK
Reducing
Agent
BOTTOM left
• F2 + 2e 2F→ -
• Eθ
F2= +2.87V
=+ve)
BOTTOM left
• F2 + 2e 2F→ -
• Eθ
F2= +2.87V
=+ve)
О
BOTTOM right
• F -
1/2F→ 2 + e
• Eθ
F2 = - 2.87V
•Oxi NOT favour (Eθ
=-ve)
BOTTOM right
• F -
1/2F→ 2 + e
• Eθ
F2 = - 2.87V
=-ve)
О
Relative strength of Oxidizing/Reducing Agent
Eθ
= +ve SEP
↓
Strong oxidizing
↓
Weak reducing agent
↓
F2 strongest
oxidizing agent
↓
F-
ion weakest
reducing agent
Eθ
= -ve SEP
↓
Weak oxidizing
↓
Strong reducing agent
↓
Li+
ion weakest
oxidizing agent
↓
Li metal strongest
reducing agent
Reaction to happen
↓
1 Oxidizing + 1 Reducing agent
(Strong) (Strong)
from both side
Reaction NEVER happen
↓
TWO Oxidizing agent
from same sides
or
TWO Reducing agent
from same sides

/V
Li+
+ e- Li↔ -3.04
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
H2O + e- H↔ 2+OH-
-0.83
Zn2+
+ 2e- Zn↔ -0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ -0.26
Sn2+
+ 2e- Sn↔ -0.14
Pb2+
+ 2e- Pb↔ -0.13
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2SO3 + H2O +0.17
Cu2+
+ 2e- ↔ Cu +0.34
1/2O2 + H2O +2e- ↔ 2OH-
+0.40
Cu+
+ e- ↔ Cu +0.52
1/2I2 + e- ↔ I-
+0.54
Fe3+
+ e- Fe↔ 2+
+0.77
Ag+
+ e- ↔ Ag +0.80
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+7H2O +1.33
1/2CI2 + e- ↔ CI-
+1.36
1/2F2 + e- ↔ F -
+2.87
TOP left
• Na+
+ e Na→
• Eθ
Na = - 2.71V
=-ve)
TOP left
• Na+
+ e Na→
• Eθ
Na = - 2.71V
=-ve)
WEAK
Oxidizing
Agent
STRONG
Oxidizing
Agent
TOP right
• Li Li→ +
+ e
• Eθ
Li = +3.04V
=+ve)
TOP right
• Li Li→ +
+ e
• Eθ
Li = +3.04V
=+ve)
STRONG
Reducing
Agent
WEAK
Reducing
Agent
BOTTOM left
• F2 + 2e 2F→ -
• Eθ
F2= +2.87V
=+ve)
BOTTOM left
• F2 + 2e 2F→ -
• Eθ
F2= +2.87V
=+ve)
BOTTOM right
• Ag Ag→ +
+ e
• Eθ
Ag = - 0.80V
=-ve)
BOTTOM right
• Ag Ag→ +
+ e
• Eθ
Ag = - 0.80V
=-ve)
О
ОО
Rxn feasible
Rxn not feasible
Rxn not feasible
Rxn feasible
О

Reaction to happen
↓
(Strong) (Strong)
from both side
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
Zn2+
+ 2e- Zn↔ -0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ -0.26
Sn2+
+ 2e- Sn↔ -0.14
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2SO3 + H2O +0.17
Cu2+
+ 2e- ↔ Cu +0.34
1/2O2 + H2O +2e- ↔ 2OH-
+0.40
1/2I2 + e- ↔ I-
+0.54
Fe3+
+ e- Fe↔ 2+
+0.77
Ag+
+ e- ↔ Ag +0.80
Pb2+
+ 2e- Pb↔ -0.13
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+1.33
1/2CI2 + e- ↔ CI-
+1.36
1/2F2 + e- ↔ F -
+2.87
WEAK
Oxidizing
Agent
STRONG
Reducing
Agent
О
Zsign
Zn Zn↔ 2+
+ 2e Eθ
= +0.76V
Sn2+
+ 2e Sn E↔ θ
= -0.14V
Zn + Sn2+
Zn→ 2+
+ Sn Eθ
= +0.62V
Rxn bet Zn + Sn2+
Will it happen ?
Eθ
= +0.62V
+ve (spontaneous)
О
О
О
Zsign
Reaction to happen
↓
(Strong) (Strong)
from both side
Rxn bet CI2 + I-
Will it happen ?
2I-
I↔ 2 + 2e Eθ
= -0.54V
CI2 + 2e 2CI↔ -
Eθ
= +1.36V
CI2 + 2I-
2CI→ -
+ I2 Eθ
= +0.82V
Eθ
= +0.82V
+ve (spontaneous)
Zn CI2

Both gaining electron
NON spontaneous
/V
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Mn2+
+ 2e- Mn↔ -1.19
Zn2+
+ 2e- Zn↔ -0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ -0.26
Sn2+
+ 2e- Sn↔ -0.14
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2SO3 + H2O +0.17
Cu2+
+ 2e- ↔ Cu +0.34
1/2O2 + H2O +2e- ↔ 2OH-
+0.40
I2 + e- ↔ I-
+0.54
Fe3+
+ e- Fe↔ 2+
+0.77
Ag+
+ e- ↔ Ag +0.80
Pb2+
+ 2e- Pb↔ -0.13
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+7H2O +1.33
CI2 + e- ↔ CI-
+1.36
1/2F2 + e- ↔ F -
+2.87
WEAK
Oxidizing
Agent
STRONG
Oxidizing
Agent
STRONG
Reducing
Agent
WEAK
Reducing
Agent
О
О
Rxn bet CI2 + I2
Will it happen ?
ОRxn NEVER happen
↓
TWO Oxidizing agent
from same sides
Rxn NEVER happen
↓
TWO Reducing agent
from same sides
Rxn bet Zn + Sn
Will it happen ?
Both losing electron
NON spontaneous
О
Rxn NEVER happen
↓
(WEAK) (WEAK)
from both side
Rxn bet Mg + K +
Will it happen ?
О
ОEθ
= -ve
-ve (Non spontaneous)

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
Salt Bridge Flow
electrons
-e -e
Zn/Cu half cells
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Eθ
cell = +0.34 – (-0.76) = +1.10V
Zn 2+
= -0.76V
Cu2+
+ 2e Cu (cathode) E↔ θ
= +0.34V
Find Eθ
cell (use formula)
Zn + Cu2+
Zn→ 2+
+ Cu Eθ
= ?????
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Zn 2+
+ 2e Zn E↔ θ
= -0.76V
Cu2+
+ 2e Cu E↔ θ
= +0.34V
Zn Zn↔ 2+
+ 2e Eθ
= +0.76
Cu2+
+ 2e Cu E↔ θ
= +0.34
Zn + Cu2+
Zn→ 2+
+ Cu Eθ
= +1.10V
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
H2O + e- 1/2H↔ 2 + OH-
-0.83
Zn2+
+ 2e- Zn↔ - 0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ -0.26
Sn2+
+ 2e- Sn↔ -0.14
Pb2+
+ 2e- Pb↔ -0.13
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2SO3 + H2O +0.17
Cu2+
+ 2e- ↔ Cu + 0.34
1/2O2 + H2O +2e- ↔ 2OH-
+0.40
Cu+
+ e- ↔ Cu +0.52
1/2I2 + e- ↔ I-
+0.54
Fe3+
+ e- ↔ Fe2+
+0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+ 7H2O +1.33
1/2CI2 + e- ↔ CI-
+1.35
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
1/2F2 + e- ↔ F +2.87
+
+1.10 V
Eθ
Zn/Cu = 1.10V
Cu2+
-
-
-
-
Zn Cu
+
+
+
+
Find Eθ using std electrode potential data for Zn/Cu half cell

Cu half cell (-ve)
Oxidation
Ag half cell (+ve)
Reduction
Anode Cathode
Cu(s) | Cu2+
(aq) || Ag+
(aq) | Ag (s)
Anode Cathode
Half Cell Half Cell
Salt Bridge Flow
electrons
-e -e
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Eθ
cell = +0.80 – (+0.34) = +0.46V
Cu 2+
+ 2e Cu (anode) E↔ θ
= +0.34V
Ag+
= +0.80V
Find Eθ
cell (use formula)
Cu + 2Ag+
Cu→ 2+
+ 2Ag Eθ
= ?????
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Cu 2+
+ 2e Cu E↔ θ
= +0.34V
Ag+
+ e Ag E↔ θ
= +0.80V
Cu Cu↔ 2+
+ 2e Eθ
= -0.34
2Ag+
+ 2e 2Ag E↔ θ
= +0.80
Cu + 2Ag+
Cu→ 2+
+ 2Ag Eθ
= +0.46V
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
H2O + e- 1/2H↔ 2 -0.83
Zn2+
+ 2e- Zn↔ -0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ -0.26
Sn2+
+ 2e- Sn↔ -0.14
Pb2+
+ 2e- Pb↔ -0.13
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2SO3 + H2O +0.17
Cu2+
+ 2e- ↔ Cu +0.34
1/2O2 + H2O +2e- ↔ 2OH-
+0.40
Cu+
+ e- ↔ Cu +0.52
1/2I2 + e- ↔ I-
+0.54
Fe3+
+ e- ↔ Fe2+
+0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+ 7H2O +1.33
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
1/2F2 + e- ↔ F +2.87
+
+0.46V
AgCu
Cu2+
Eθ
Cu/Ag = 0.46V
Ag+
-
-
-
-
+
+
+
+
Find Eθ using std electrode potential data for Cu/Ag half cell

Mn half cell (-ve)
Oxidation
Ni half cell (+ve)
Reduction
Anode Cathode
Mn(s) | Mn2+
(aq) || Ni2+
(aq) | Ni (s)
Anode Cathode
Half Cell Half Cell
Salt Bridge Flow
electrons
-e -e
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Eθ
cell = -0.26 – (-1.19) = +0.93V
Mn 2+
+ 2e Mn (anode) E↔ θ
= -1.19V
Ni2+
+ 2e Ni (cathode) E↔ θ
= -0.26V
Find Eθ
cell (use formula)
Mn + Ni2+
Mn→ 2+
+ Ni Eθ
= ?????
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Mn 2+
+ 2e Mn E↔ θ
= -1.19V
Ni2+
+ 2e Ni E↔ θ
= -0.26V
Mn Mn↔ 2+
+ 2e Eθ
= +1.19
Ni2+
+ 2e Ni E↔ θ
= -0.26
Mn + Ni2+
Mn→ 2+
+ Ni Eθ
= +0.93V
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
H2O + e- 1/2H↔ 2 + OH-
-0.83
Zn2+
+ 2e- Zn↔ -0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ - 0.26
Sn2+
+ 2e- Sn↔ -0.14
Pb2+
+ 2e- Pb↔ -0.13
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2SO3 + H2O +0.17
Cu2+
+ 2e- ↔ Cu +0.34
1/2O2 + H2O +2e- ↔ 2OH-
+0.40
Cu+
+ e- ↔ Cu +0.52
1/2I2 + e- ↔ I-
+0.54
Fe3+
+ e- ↔ Fe2+
+0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+ 7H2O +1.33
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
1/2F2 + e- ↔ F +2.87
+
+0.93 V
Eθ
Mn/Ni = 0.93V
Ni2+
-
-
-
-
NiMn
+
+
+
+Mn2+
2 Uses of Standard Electrode Potential (SEP) Data
Find Eθ using std electrode potential data for Mn/Ni half cell

Eθ
= -0.20V
-ve (NON spontaneous)
Reaction to happen
↓
(Strong) (Strong)
from both side
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
Zn2+
+ 2e- Zn↔ -0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ -0.26
Sn2+
+ 2e- Sn↔ -0.14
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
Cu2+
+ 2e- ↔ Cu +0.34
1/2O2 + H2O +2e- ↔ 2OH-
+0.40
Cu+
+ e- ↔ Cu +0.52
I2 + 2e- ↔ I-
+0.54
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- Br↔ -
+1.07
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+7H2O +1.33
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- Mn↔ 2+
+ 4H2O +1.51
1/2F2 + e- ↔ F -
+2.87
WEAK
Oxidizing
Agent
STRONG
Oxidizing
Agent
STRONG
Reducing
Agent
WEAK
Reducing
Agent
О
Z
Zn Zn↔ 2+
+ 2e Eθ
= +0.76
Sn2+
+ 2e Sn E↔ θ
= -0.14
Zn + Sn2+
Zn→ 2+
+ Sn Eθ
= +0.62V
Rxn bet Zn + Sn2+
Will it happen ?
Eθ
= +0.62V
+ve (spontaneous)
↓
(WEAK) (WEAK)
from both side
Rxn bet Cu2+
+I-
Will it happen ?
О
Rxn feasible
О
О
2I-
I↔ 2 + 2e Eθ
= -0.54
Cu2+
+ 2e Cu E↔ θ
= +0.34
2I-
+ Cu2+
Cu→ + I2 Eθ
= -0.20V
Eθ
= -0.20V
Rxn not feasible
Zn(s) | Zn2+
(aq) || Sn2+
(aq) | Sn (s)
Anode Cathode
Find Eθ
cell (use formula)
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Eθ
cell = -0.14 – (-0.76) = +0.62V
Eθ
= +0.62V
+ve (spontaneous)
Pt(s) | I-
, I2 || Cu2+
(aq) | Cu (s)
Anode Cathode
Find Eθ
cell (use formula)
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Eθ
cell = +0.34 – (+0.54) = -0.20V
Determine spontaneity rxn. Will it HAPPEN ?

Eθ
= -0.82V
Reaction to happen
↓
(Strong) (Strong)
from both side
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
Zn2+
+ 2e- Zn↔ -0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ -0.26
Sn2+
+ 2e- Sn↔ -0.14
Pb2+
+ 2e- Pb↔ -0.13
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2SO3 +0.17
Cu2+
+ 2e- ↔ Cu +0.34
I2 + 2e- ↔ I-
+0.54
Fe3+
+ e- Fe↔ 2+
+0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- Br↔ -
+1.07
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+7H2O +1.33
1/2CI2 + e- ↔ CI-
+1.36
1/2F2 + e- ↔ F -
+2.87
WEAK
Oxidizing
Agent
STRONG
Oxidizing
Agent
STRONG
Reducing
Agent
WEAK
Reducing
Agent
О
Z
Zn Zn↔ 2+
+ 2e Eθ
= +0.76
Cu2+
+ 2e Cu E↔ θ
= +0.34
Zn + Cu2+
Zn→ 2+
+Cu Eθ
= +1.10V
Rxn bet Zn + Cu2+
Will it happen ?
Eθ
= +1.10V
+ve (spontaneous)
↓
(WEAK) (WEAK)
from both side
Rxn bet I2 +CI-
Will it happen ?
О
Rxn feasible
О
О
2CI-
CI↔ 2 + 2e Eθ
= -1.36
I2 + 2e 2I↔ -
Eθ
= +0.54
I2 + 2CI-
2I-→ + CI2 Eθ
= -0.82V
Eθ
= -0.82V
Rxn not feasible
Zn(s) | Zn2+
(aq) || Cu2+
(aq) | Cu (s)
Anode Cathode
Find Eθ
cell (use formula)
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Eθ
cell = 0.34 – (-0.76) = +1.10V
Eθ
= +1.10V
+ve (spontaneous)
Pt(s) | CI-
, CI2 || I2 I-
| Pt (s)
Anode Cathode
Find Eθ
cell (use formula)
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Eθ
cell = +0.54 – (+1.36) = -0.82V

Eθ
= -0.59V
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI↔ -1.66
Mn2+
+ 2e- Mn↔ -1.19
H2O + e- H↔ 2 + OH-
-0.83
Zn2+
+ 2e- Zn↔ -0.76
Fe2+
+ 2e- Fe↔ -0.45
Ni2+
+ 2e- Ni↔ -0.26
Sn2+
+ 2e- Sn↔ -0.14
H+
+ e- 1/2H↔ 2 0.00
Cu2+
+ e- Cu↔ +
+0.15
SO4
2-
+ 4H+
+ 2e- H↔ 2S +0.17
Cu2+
+ 2e- ↔ Cu +0.34
Cu+
+ e- Cu↔ +0.52
Fe3+
+ e- Fe↔ 2+
+0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- Br↔ -
+1.07
1/2O2 + 2H+
+2e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+1.33
1/2CI2 + e- ↔ CI-
+1.36
1/2F2 + e- ↔ F -
+2.87
WEAK
Oxidizing
Agent
STRONG
Oxidizing
Agent
STRONG
Reducing
Agent
WEAK
Reducing
Agent
Cu Cu↔ 2+
+ 2e Eθ
= -0.34
2H+
+ 2e H↔ 2 Eθ
= +0.00
Cu + 2H+
Cu→ 2+
+H2 Eθ
= -0.34V
Rxn bet Cu + H+
Will it happen ?
Eθ
= -0.34V
↓
(WEAK) (WEAK)
from both side
Rxn bet Fe3+
+CI-
Will it happen ?
О
О
О
2CI-
CI↔ 2 + 2e Eθ
= -1.36
2Fe3+
+ 2e 2Fe↔ 2+
Eθ
= +0.77
2Fe3+
+ 2CI-
2Fe→ 2+
+CI2 Eθ
= -0.59V
Eθ
= -0.59V
Rxn not feasible
Cu(s) | Cu2+
(aq) || H+
H2 | Pt (s)
Anode Cathode
Find Eθ
cell (use formula)
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Eθ
cell = 0.00 – (+0.34) = -0.34V
Eθ
= -0.34V
-ve (spontaneous)
Pt(s) | CI-
, CI2 || Fe3+
,Fe2+
|Pt (s)
Anode Cathode
Find Eθ
cell (use formula)
Eθ
cell = Eθ
(cathode) – Eθ
(anode)
Eθ
cell = +0.77 – (+1.36) = -0.59V
О
Rxn not feasible
↓
(WEAK) (WEAK)
from both side

Eθ
value DO NOT depend surface area of metal electrode.
EMF = Energy per unit charge. (Joule)/C
EMF 10v = 10J energy released by 1C of charge flowing
= 100J energy released by 10C of charge flowing
Eθ
– intensive property– independent of amt – ratio energy/charge
Increasing surface area metal will NOT increase EMF
Eθ
Zn/Cu = 1.10V
Surface area exposed 10 cm2
Total charges 100C leave electrode
EMF = 1.10V = 1.1 J energy for 1 C (charges leaving)
1C release 1.1J energy
100 C release 110 J energy
Voltmeter measure energy for 1C – 110J/100C – 1.1V
EMF no change
Current – measured in Amperes or Coulombs per second
1A = 1 Coulomb charge pass through a point in 1 second = 1C/s
1 Coulomb charge (electron) = 6.28 x 10 18
electrons passing in 1 second
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
ond
electron
ond
Coulomb
A
sec.1
.1028.6
sec1
1
1
18
×
==
Surface area increase ↑
Total Energy increase ↑
Total Charge increase ↑Current increase ↑
BUT EMF remain SAME
EMF = (Energy/charge)
t
Q
I
tIQ
=
×=
Q up ↑ – I up ↑
100C flow
110J released
VEMF
EMF
eCh
Energy
EMF
10.1
100
110
arg
=
=
=
Surface area exposed 100cm2
Total charges 1000C leave electrode
EMF = 1.10V = 1.1 J energy for 1 C (charges leaving)
1C release 1.1J energy
1000 C release 1100 J energy
Voltmeter measure energy for 1C – 1100J/1000C – 1.1V
EMF no change
VEMF
EMF
eCh
Energy
EMF
10.1
1000
1100
arg
=
=
=
Eθ
Zn/Cu = 1.10V
1000C flow
1100J released
t
Q
I =
t
Q
I =

Iron rust in presence of water + oxygen
Iron galvanized/coated with zinc.
/V
Zn2+
+ 2e- Zn↔ - 0.76
Fe2+
+ 2e- ↔ Fe -0.44
O2 + 2H2O + 4e ↔ 4OH-
+0.40
Iron rusting
Rusting Process happen
Eθ
/V
Fe2+
+ 2e- ↔ Fe -0.44
O2 + 2H2O + 4e ↔ 4OH-
+0.40
O2 + 4H+
+ 4e ↔ 2H2O + 1.23
H2O + O2 less reactive (cathode region) – reduction – gain e
Fe more reactive (anode region) – oxidation - lose e
OxidationReduction
Fe2+
+ 2e- Fe -0.44↔
O2 +2H2O+4e ↔ 4OH-
+0.40
Fe Fe↔ 2+
+ 2e Eθ
= +0.44
O2+2H2O+4e ↔ 4OH-
Eθ
= +0.40
2Fe+O2 +2H2O→2Fe2+
+4OH-
Eθ
= +0.84V
Eθ
= +0.84V +ve (spontaneous)
О
О
Dissolve O2
in water
Dissolve O2
in acid
How galvanizing reduces rusting
Iron Galvanized
with Zn
Iron/Steel Galvanized
with tin
Zn more reactive – lose e instead of Fe
Zn as Sacrificial metal/ Cathodic Protection
Electron flow to O2/H2O region
Prevent Fe rusting/lose e
O2 gain e
Fe
O2 + 2H2O + 4e ↔ 4OH-
flow e-
Zn oxidation/lose e
Zn2+
+ 2e- ↔ Zn -0.76
O2 +2H2O+4e ↔ 4OH-
+0.40
Zn lose e- (Stronger RA)
Zn ↔ Zn2+
+ 2e Eθ
= +0.76
O2+2H2O+4e ↔ 4OH-
Eθ
= +0.40
2Zn+O2 +2H2O→2Zn2+
+4OH-
Eθ
= +1.16V
Eθ
= +1.16 +ve (spontaneous)
water
О
О
Anodic region
Cathodic region
Zn Zn
FeFeFe

Eθ
Iron rust in presence of water + oxygen
Iron can coated with tin widely used in canning
Tin corrodes less readily than iron (protect iron)
/V
Fe2+
+ 2e- ↔ Fe -0.44
Sn2+
+ 2e- Sn -0.14↔
O2 + 2H2O + 4e ↔ 4OH-
+0.40
Iron rusting
If tin coat broken, iron rust faster as it will displace tin ions from its solution
Will iron rust spontaneously, if Sn2+
(tin ions) are formed.
Rusting Process happen
Eθ
/V
Fe2+
+ e- ↔ Fe -0.44
O2 + 2H2O + 4e ↔ 4OH-
+0.40
O2 + 4H+
+ 4e ↔ 2H2O + 1.23
H2O + O2 less reactive (cathode region) – reduction – gain e
Fe more reactive (anode region) – oxidation - lose e
OxidationReduction
Fe2+
+ 2e- Fe -0.44↔
O2 +2H2O+4e ↔ 4OH-
+0.40
Fe Fe↔ 2+
+ 2e Eθ
= +0.44
O2+2H2O+4e ↔ 4OH-
Eθ
= +0.40
2Fe+O2 +2H2O 4Fe→ 2+
+4OH-
Eθ
= +0.84V
Eθ
О
О
Dissolve O2
in water
How coating reduces rusting
Iron/Steel coated with tin/Sn
BUT if it is exposed - Fe will rust
Fe more reactive Sn
Tin/Sn protect Fe metal
Electron flow Fe to O2/H2O region
water
Fe oxidation/lose e
flow e-
O2 + 2H2O + 4e ↔ 4OH-
Iron metal
water
O2 gain e
Sn Sn2+
/V
Fe2+
+ 2e- ↔ Fe -0.44
Sn2+
+ 2e- Sn -0.14↔
O2 + 2H2O + 4e ↔ 4OH-
+0.40
Fe Fe↔ 2+ + 2e Eθ = +0.44
O2+2H2O+4e ↔ 4OH-
Eθ
= +0.40
2Fe+O2 +2H2O 4Fe→ 2+
+4OH-
Eθ
= +0.84V
Fe Fe↔ 2+ + 2e Eθ = +0.44
Sn2+
+ 2e ↔ Sn Eθ
= -0.14
Fe + Sn2+
→ Fe2+
+ Sn Eθ
= +0.30V
Eθ
О
О
О
О
Sn SnSn
FeFeFe Fe

State which is able to convert Fe2+
to Fe3+
/V
AI3+
+ 3e- AI -1.66↔
I2 + 2e- ↔ 2I-
+0.54
Fe3+
+ e- ↔ Fe2+
+0.77
H2O2 + 2H+
+ 2e ↔ 2H2O +1.07
Co3+
+ e ↔ Co2+
+1.51
2Fe2+
2Fe↔ 3+
+ 2e Eθ
= -0.77
H2O2 + 2H+
+ 2e 2H↔ 2O Eθ
=+1.07
2Fe2+
+ H2O2 + 2H+
2Fe→ 3+
+ 2H2O Eθ
= +0.30V
Eθ
Fe2+
Fe↔ 3+
+ e Eθ
= -0.77
Co3+
+ e ↔ Co 2+
Eθ
=+1.51
Fe2+
+ Co3+
Fe→ 3+
+ Co2+
Eθ
= +0.74V
Eθ
Eθ
cell = EMF in V (std condition)
Eθ
= Show ease/tendency of species to accept/lose electron
Eθ
= +ve std electrode potential = stronger oxidizing agent – weaker reducing agent – accept e
Eθ
= - ve std electrode potential = stronger reducing agent - weaker oxidizing agent – lose e
Eθ value DO NOT depend on stoichiometric coefficient. EMF = Energy per unit charge. (Joule)/C
EMF 10v = 10J energy released by 1C of charge flowing
= 100J energy released by 10C of charge flowing
Eθ
, Std electrode potential – intensive property – not dependent on amt – ratio energy/charge
Eθ
= +ve suggest rxn feasible, does not tell rate, feasible but may be slow, give no indication rate
Eθ
= +ve = Energetically feasible but kinetically non feasible
E = ↑ +ve ↑ (OA)
/V
Fe3+
+ e- ↔ Fe2+
+0.77
H2O2 +2H+
+2e ↔ 2H2O +1.07
/V
Fe3+
+ e- ↔ Fe2+
+0.77
Co3+
+ e ↔ Co2+
+1.51
Stronger OA
Strongest OA
Redox Question
Aluminium air battery
Excellent Zn/Cu gravity cell for IA
Zinc air battery
Videos on battery making

Arrange the species in order of
increasing oxidizing/reducing strength
/V
Zn2+
+ 2e- Zn -0.76↔
Br2 + 2e- ↔ 2Br-
+1.07
I2 + 2e- ↔ 2I-
+0.54
Fe3+
+ e- ↔ Fe2+
+0.77
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
Oxidizing agent (OA)
MnO4
_
> Br2 > Fe3+
> I2 > Zn2+
Reducing agent (RA)
Zn > I-
> Fe 2+
> Br-
> Mn2+
Arrange in order of increasing reducing strength.
(Strongest reducing agent)
Redox Questions
1 2
E = most +ve ↑
strongest OA
E = most -ve ↑
strongest RA
/V
Zn2+
+ 2e- Zn -0.76↔
I2 + 2e- ↔ 2I-
+0.54
Fe3+
+ e- ↔ Fe2+
+0.77
Br2 + 2e- ↔ 2Br-
+1.07
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
arrange increasing ↑ E value
E = ↑ +ve ↑ (OA)
Eθ
/V
X 3+
+ 3e- X -1.56↔
Y 2+
+ 2e- Y -2.70↔
Z 2+
+ 2e- Z +0.90↔
E = ↑ -ve ↑(RA)
E = most -ve ↑
strongest RA
Reducing agent
Y > X > Z
arrange increasing ↑ E value
Eθ
/V
Y 2+
+ 2e- Y -2.70↔
X 3+
+ 3e- X -1.56↔
Z 2+
+ 2e- Z +0.90↔
E = ↑ -ve ↑ (RA)
4433
/V
Ti2+
+ 2e- Ti -1.63↔
2H+
+ 2e- H↔ 2 0.00
Rxn bet Ti + H+
Will it happen ?
Ti Ti↔ 2+
+ 2e Eθ
= +1.63
2H+
+ 2e H↔ 2 Eθ
= 0.00
Ti + 2H+
Ti→ 2+
+ H2 Eθ
= +1.63V
Eθ
= +1.63V
+ve (spontaneous)
What happen when gold added to acid
/V
2H+
+ 2e- H↔ 2 0.00
Au3+
+ 3e ↔ Au +1.58
Rxn bet Au + H+
Will it happen ?
What happen when titanium added to acid
2Au 2↔ Au3+
+ 6e Eθ
= -1.58
6H+
+ 6e 3H↔ 2 Eθ
= 0.00
2Au + 6H+
2Au→ 3+
+ 3H2 Eθ
= -1.58V
Eθ
= -1.58V
-ve ( NON spontaneous)
acid acid

Redox Question
6Predict if manganate will oxidize chloride ion?
MnO2 + 4H+
+ 2CI-
Mn→ 2+
+ 2H2O + CI2 Eθ
= ?
55
MnO2 +4H+
+ 2e- Mn↔ 2+
+ 2H2O +1.23
1/2CI2 + e- ↔ CI-
+1.36
2CI-
CI↔ 2 + 2e Eθ
= -1.36
MnO2 + 4H+
+ 2e Mn↔ 2+
+ 2H2O Eθ
= +1.23
MnO2 + 4H+
+2CI-
Mn→ 2+
+2H2O+CI2 Eθ
= -0.13V
Eθ
= -0.13V -ve (NON spontaneous)
/V
Cr2O7
2-
+ 14H+
+ 6e- ↔ 2Cr3+
+ 7H2O +1.33
MnO2 +4H+
+ 2e- Mn↔ 2+
+ 2H2O +1.23
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
Predict if MnO4
-
able to oxidize aq CI-
to CI2
2MnO4 + 16H+
+ 10CI-
2Mn→ 2+
+ 8H2O + 5CI2
E = ↑ +ve ↑ (OA)О
О
/V
Cr2O7
2-
+ 14H+
+ 6e- ↔ 2Cr3+
+ 7H2O +1.33
MnO2 +4H+
+ 2e- Mn↔ 2+
+ 2H2O +1.23
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
О
О
2CI-
CI↔ 2 + 2e Eθ
= -1.36
MnO4
-
+ 8H+
+ 5e Mn↔ 2+
+ 4H2O Eθ
= +1.51
2MnO4 + 16H+
+10CI-
2Mn→ 2+
+8H2O+5CI2 Eθ
= +0.15V
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
Eθ
Predict if iron react with HCI a) absence air
Which is stronger OA ?
Fe Fe↔ 2+
+ 2e Eθ
= +0.44
2H+
+ 2e H↔ 2 Eθ
= 0.00V
Fe + 2H+
Fe→ 2+
+ H2 Eθ
= +0.44V
Eθ
/V
Fe2+
+ 2e- Fe -0.44↔
2H+
+ 2e- H↔ 2 0.00
O2 +2H2O+4e ↔ 4OH-
+0.40
Fe Fe↔ 2+
+ 2e Eθ
= +0.44
O2+2H2O+4e ↔ 4OH-
Eθ
= +0.40
2Fe+O2 +2H2O→2Fe2+
+4OH-
Eθ
= +0.84V
Predict if iron react with HCI b) presence of air
Fe2+
+ 2e- Fe -0.44↔
2H+
+ 2e- H↔ 2 0.00
О
О
Fe2+
+ 2e- Fe -0.44↔
O2 +2H2O+4e ↔ 4OH-
+0.40
О
О
/V
Fe2+
+ 2e- Fe -0.44↔
2H+
+ 2e- H↔ 2 0.00
O2 +2H2O+4e ↔ 4OH-
+0.40
Eθ
Iron rusting
E = ↑ +ve
↑ (OA)

Acknowledgements
Thanks to source of pictures and video used in this presentation
Thanks to Creative Commons for excellent contribution on licenses
http://creativecommons.org/licenses/
http://spmchemistry.onlinetuition.com.my/2013/10/electrolytic-cell.html
http://www.chemguide.co.uk/physical/redoxeqia/introduction.html
http://educationia.tk/reduction-potential-table
http://2012books.lardbucket.org/books/principles-of-general-chemistry-v1.0/s23-
electrochemistry.html
http://wps.prenhall.com/wps/media/objects/4680/4792445/ch18_10.htm
Prepared by Lawrence Kok
Check out more video tutorials from my site and hope you enjoy this tutorial
http://lawrencekok.blogspot.com

IB Chemistry on Standard Reduction Potential, Standard Hydrogen Electrode and Electrochemical Series

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