IB Chemistry on Electrolysis and Faraday's Law

1. http://lawrencekok.blogspot.com
Prepared by
Lawrence Kok
Tutorial on Electrolysis and Faraday’s Law.

2. Types voltaic cell
Conversion electrical energy
to chemical energy
Electrochemistry
Electrolytic cellVoltaic cell
NH4CI and ZnCI2
Chemical and electrical energy
Redox rxn
(Oxidation/reduction)
Movement electron
Produce electricity
Conversion chemical energy
to electrical energy
Electrodes – different metal (Half cell) Electrodes – same metal (Half cell)
Chemical
rxn
Electric current
Daniell cell Alkaline cellDry cell Nickel cadmium cell
Primary cell (Non rechargeable)
MnO2 and KOH
Secondary cell (Rechargeable)

3. Conversion electrical to chemical energy
Electrochemistry
Electrolytic cellVoltaic cell
Conversion chemical to electrical energy
Cathode (+ve) - Reduction Cathode (-ve) - Reduction
Vs
Electron flow from anode (-ve) to cathode (+ve) electrode Electron flow from anode (+ve) to cathode (-ve) electrode
Anode
(-ve)
Spontaneous rxn Non Spontaneous rxn
Anode (-ve) – Oxidation Anode (+ve) – Oxidation
++
О
О
О
О
- -
Zn → Zn 2+
+ 2e
(oxidized)
Cu2+
+ 2e → Cu
(reduced)
Zn2+
Zn2+
Zn2+
Zn2+-
-
-
-
→ +
+
+
Cu2+
Cu2+
Cu2+
-e
-e
+
+
+ -
-
-
X-
X + -e→
(oxidized)
X
-
X
-
X
-
Anode
(+ve)
Cathode
(-ve)
Cathode
(+ve)
-e
-e
Y+
+ e- Y→
(reduced)
Y+
Y+
Y+-e
-e
-e
-e
Anode Cathode
Voltaic Cell Electrolytic Cell
Anode Oxidation Negative (-ve) Oxidation Positive (+ve)
Cathode Reduction Positive (+ve) Reduction Negative (-ve)
Cation (+ve ion) to cathode (-ve)Anion (-ve ion) to anode (+ve)

4. Zn → Zn 2+
+ 2e
Conversion electrical to chemical energy
Electrochemistry
Conversion chemical to electrical energy
Cathode (-ve)
Reduction
Vs
Electron flow from anode (-ve) to cathode (+ve) electrode Electron flow from anode (+ve) to cathode (-ve) electrode
Anode
(-ve)
Spontaneous rxn Non Spontaneous rxn
Anode (+ve)
Oxidation
+
О
О
-
Zn → Zn 2+
+ 2e
(oxidized)
Cu2+
+ 2e → Cu
(reduced)
Zn2+
Zn2+
Zn2+
Zn2+
-
--
-→ + +
+
Cu2+
Cu2+
Cu2+
-e
-e +
+
+
-
-
-
2Br-
Br→ 2 + 2e-
(oxidized)
Br
-
Br
-
Br
-
Anode
(+ve)
Cathode
(-ve)Cathode
(+ve)
-e
-e
Pb2+
+ 2e- Pb→
(reduced)
Pb2+
-e
-e
-e
Cation (+ve ion) to cathode (-ve)Anion (-ve ion) to anode (+ve)
1.10Volt -e -e
-
-
-
-
+
+
+
+
Anode Cathode
Zn half cell (-ve)
Oxidation
Cu half cell (+ve)
Reduction
Cu2+
+ 2e → Cu
Zn + Cu2+
→ Zn2+
+ Cu
2Br- → Br2 + 2e
Zn/Cu Voltaic Cell PbBr2 molten Electrolytic Cell
Pb2+
+ 2e → Pb
PbBr2 → Pb+ Br2
Br -
Br -
Br -
Pb2+
Pb2+
Pb2+
Pb2+
Pb2+

5. Conversion electrical to chemical energy
Electrochemistry
Conversion chemical to electrical energy
Cathode (-ve)
Reduction
Vs
Spontaneous rxn Non Spontaneous rxn
Anode (+ve)
Oxidation
+
О
О
-
-e
1.10 Volt
-e -e
-
-
-
-
+
+
+
+
Anode Cathode
Zn/Cu Voltaic Cell PbBr2 molten Electrolytic Cell
PbBr2 Pb→ + Br2 Eθ
= ???
Br -
Br -
Br -
Pb2+
Pb2+
Pb2+
Find Eθ
cell (use reduction potential)
Zn 2+
+ 2e Zn E↔ θ
= -0.76V
Cu2+
+ 2e Cu E↔ θ
= +0.34V
Cu half cell (+ve)
Reduction
Zn half cell (-ve)
Oxidation
Zn + Cu2+
Zn→ 2+
+ Cu Eθ
= ?????
Zn Zn↔ 2+
+ 2e Eθ
= +0.76
Cu2+
+ 2e Cu E↔ θ
= +0.34
Zn + Cu2+
Zn→ 2+
+ Cu Eθ
= +1.10V
Eθ
= +1.10V
+ve (spontaneous)
Pb2+
+ 2e Pb E↔ θ
= -0.13V
Br-
+ e Br↔ -
Eθ
= +1.07V
Find Eθ
cell (use reduction potential)
2Br -
Br↔ 2+ 2e Eθ
= -1.07
Pb2+
+ 2e Pb E↔ θ
= -0.13
Pb2+
+ 2Br -
Pb→ +Br2 Eθ
= -1.20V
Compound broken down
(LYSIS)
energy needed
Eθ
= -1.20V
-ve (NON spontaneous)
Conversion chemical to electrical energy Conversion electrical to chemical energy
Energy needed to decompose compound!!!!!!!!

6. Discharge of ions
1 Cation + 1 Anion
Electrolysis (Molten Salt)
Oxidation ← Anode (+ve) ← Anion
PbBr2 molten Electrolytic Cell
Eθ
=-ve → supply +1.20v to breakdown PbBr2 Pb→ + Br2
Find Eθ
cell (use reduction potential)
Pb2+
+ 2e Pb E↔ θ
= -0.13
2Br -
Br↔ 2+ 2e Eθ
= -1.07
Pb2+
+ 2Br -
Pb→ +Br2 Eθ
= -1.20V
Eθ
= -1.20V
-ve (NON spontaneous)
Conversion electrical to chemical energy
Energy needed to decompose compound!!!!!!!!
Cation → Cathode (-ve) → Reduction
Liquid – Pb2+
and Br-
ions
+
+
+
+
+
+
-
-
-
-
-
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 + 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↔
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
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
Discharged Br-
ion Br2 gas (brown gas seen) Discharged Pb2+
ion to Pb (grey deposit)
2Br -
Br↔ 2+ 2e Pb2+
+ 2e Pb↔
Compound broken down
(LYSIS)
energy needed
О
О
Eθ
Oxidation = -1.07
E
θ Reduction =
-0.13
Pb2+
Br -
Factor affecting ion discharged
(Selective Discharge)
↓
- Molten/aqueous
- Relative E values of ion
- Conc ion – conc/diluted
- Nature of electrode
Inert electrode
Carbon/graphite
Br -
Br -
Br -
Pb2+
Pb2+
Pb2+

7. Discharge of ions
1 Cation + 1 Anion
Oxidation ← Anode (+ve) ← Anion
CaCI2 molten Electrolytic Cell
Find Eθ
cell (use reduction potential)
Ca2+
+ 2e Ca E↔ θ
= -2.87
2CI -
CI↔ 2+ 2e Eθ
= -1.36
Ca2+
+ 2CI -
Ca→ +CI2 Eθ
= -4.23V
Eθ
= -4.23V
-ve (NON spontaneous)
Conversion electrical to chemical energy
Energy needed to decompose compound!!!!!!!!
Cation → Cathode (-ve) → Reduction
Liquid – Ca2+
and CI-
ions
+
+
+
+
+
+
-
-
-
-
-
Oxidized sp ↔ Reduced sp Eθ
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Ca2+
+ 2e- Ca↔ -2.87
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
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
Discharged CI-
ion CI2 gas (yellow gas) Discharged Ca2+
ion to Ca
2CI -
CI↔ 2+ 2e Ca2+
+ 2e Ca↔
Compound broken down
(LYSIS)
energy needed
О
О
Eθ
Oxidation = -1.36
Eθ
Reduction
=
-2.87
Ca2+
CI -
Eθ
=-ve → supply +4.23v to breakdown CaCI2 Ca→ + CI2
Electrolysis (Molten Salt)
Factor affecting ion discharged
(Selective Discharge)
↓
- Molten/aqueous
- Relative E values of ion
- Conc ion – conc/diluted
- Nature of electrode
Inert electrode
Carbon/graphite
CI -
CI -
CI -
Ca2+
Ca2+
Ca2+

8. Discharge of ions
2 Cation + 2 Anion
Oxidation ← Anode (+ve) ← Anion
NaCI aqueous Electrolytic Cell
2H+
+ 2e H↔ 2 Eθ
= -0.83
4OH -
2H↔ 2O + O2 + 4e Eθ
= -1.23
2H2O 2H→ 2 + O2 Eθ
= -2.06V
Eθ
= -2.06V
-ve (NON spontaneous)
Conversion electrical to chemical energy
Energy needed to decompose compound!!!!!!!!
Cation → Cathode (-ve) → Reduction
Na+
, CI-
+ H+
, OH-
(from water)
+
+
+
+
+
+
-
-
-
-
-
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
Al3+
+ 3e- AI -1.66↔
Mn2+
+ 2e- Mn -1.19↔
2H2O +2e- H↔ 2 + 2OH-
-0.83
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
O2 + 4H+
+4e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+1.33
1/2CI2 + e- ↔ CI-
+1.36
1/2F2 + e- ↔ F-
+2.87
Discharged OH-
ion O2 gas Discharged H+
ion to H2 gas
О
О
Na+
/H+
CI-
/OH-
Eθ
=-ve → supply +2.06v to breakdown NaCI H→ 2 + O2
Electrolysis (Aqueous Salt)
Factor affecting ion discharged
(Selective Discharge)
↓
- Molten/aqueous
- Relative E values of ion
- Conc ion – conc/diluted
- Nature of electrode
Reduction
Eθ
> more +ve easier gain e
Na+
+ e Na E↔ θ
= -2.71
2H+
+ 2e H↔ 2 Eθ
= -0.83
2H2O +2e- H↔ 2 + 2OH-
Eθ
= -0.83
О
Oxidation
Eθ
> more +ve easier to lose e
4OH-
2H↔ 2O + O2 + 4e Eθ
= -1.23
2H2O 4H↔ +
+ O2 + 4e Eθ
= -1.23
2CI-
CI↔ 2 + 2e Eθ
= -1.36
О
Inert electrode
Carbon/graphite
OH-
OH-
CI -
CI -
H+
H+
Na+
Na+

9. Discharge of ions
2 Cation + 2 Anion
Oxidation ← Anode (+ve) ← Anion
NaI aqueous Electrolytic Cell
2H+
+ 2e H↔ 2 Eθ
= -0.83
2I -
I↔ 2 + 2e Eθ
= -0.54
NaI H→ 2 + I2 Eθ
= -1.37V
Eθ
= -1.37V
-ve (NON spontaneous)
Conversion electrical to chemical energy
Energy needed to decompose compound!!!!!!!!
Cation → Cathode (-ve) → Reduction
Na+
, I-
+ H+
, OH-
(from water)
+
+
+
+
+
+
-
-
-
-
-
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
Al3+
+ 3e- AI -1.66↔
Mn2+
+ 2e- Mn -1.19↔
2H2O +2e- H↔ 2 + 2OH-
-0.83
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
I2 + 2e- ↔ 2I-
+0.54
Fe3+
+ e- ↔ Fe2+
+0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
O2 + 4H+
+4e- ↔ H2O +1.23
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
1/2F2 + e- ↔ F-
+2.87
Discharged I-
ion I2 Discharged H+
ion to H2 gas
О
О
Na+
/H+
I-
/OH-
Eθ
= -ve → supply +1.37 v to breakdown NaI H→ 2 + I2
Electrolysis (Aqueous Salt)
Factor affecting ion discharged
(Selective Discharge)
↓
- Molten/aqueous
- Relative E values of ion
- Conc ion – conc/diluted
- Nature of electrode
Reduction
Eθ
> more +ve easier gain e
Na+
+ e Na E↔ θ
= -2.71
2H+
+ 2e H↔ 2 Eθ
= -0.83
2H2O +2e- H↔ 2 + 2OH-
Eθ
= -0.83
О
Oxidation
Eθ
> more +ve easier to lose e
2I-
I↔ 2 + 2e Eθ
= -0.54
4OH-
2H↔ 2O + O2 + 4e Eθ
= -1.23
2H2O 4H↔ +
+ O2 + 4e Eθ
= -1.23
О
Inert electrode
Carbon/graphite
I -
I -
OH-
OH-
H+
H+
Na+
Na+

10. Discharge of ions
2 Cation + 2 Anion
Oxidation ← Anode (+ve) ← Anion
CuCI2 aqueous Electrolytic Cell
Cu2+
+ 2e Cu↔ Eθ
= +0.34
4OH-
2H↔ 2O + O2 + 4e Eθ
= -1.23
CuCI2 Cu + O→ 2 Eθ
= -0.89V
Eθ
= -0.89V
-ve (NON spontaneous)
Conversion electrical to chemical energy
Energy needed to decompose compound!!!!!!!!
Cation → Cathode (-ve) → Reduction
Cu2+
, CI-
+ H+
, OH-
(from water)
+
+
+
+
+
+
-
-
-
-
-
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↔
2H2O +2e- H↔ 2 + 2OH-
-0.83
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
Cu+
+ e- ↔ Cu +0.52
I2 + 2e- ↔ 2I-
+0.54
Fe3+
+ e- ↔ Fe2+
+0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
O2 + 4H+
+4e- ↔ H2O +1.23
1/2CI2 + e- ↔ CI-
+1.36
1/2F2 + e- ↔ F-
+2.87
Discharged OH-
ion O2 Discharged Cu2+
ion to Cu metal
О
Cu2+
/H+
CI-
/OH-
Eθ
= -ve → supply +0.89 v to breakdown CuCI2 Cu→ + O2
Electrolysis (Aqueous Salt)
Factor affecting ion discharged
(Selective Discharge)
↓
- Molten/aqueous
- Relative E values of ion
- Conc ion – conc/diluted
- Nature of electrode
Reduction
Eθ
> more +ve easier gain e
2H+
+ 2e H↔ 2 Eθ
= -0.83
2H2O +2e- H↔ 2 + 2OH-
Eθ
= -0.83
Cu2+
+ 2e Cu E↔ θ
= +0.34
О
Oxidation
Eθ
> more +ve easier to lose e
4OH-
2H↔ 2O + O2 + 4e Eθ
= -1.23
2H2O 4H↔ +
+ O2 + 4e Eθ
= -1.23
2CI-
CI↔ 2 + 2e Eθ
= -1.36
ОО
Inert electrode
Carbon/graphite
OH-
OH-
CI -
CI -
H+
H+
Cu2+
Cu2+

11. Discharge of ions
2 Cation + 2 Anion
Oxidation ← Anode (+ve) ← Anion
CuBr2 aqueous Electrolytic Cell
Cu2+
+ 2e Cu↔ Eθ
= +0.34
2Br-
Br↔ 2 + 2e Eθ
= -1.07
CuBr2 Cu + Br→ 2 Eθ
= -0.73V
Eθ
= -0.73V
-ve (NON spontaneous)
Conversion electrical to chemical energy
Energy needed to decompose compound!!!!!!!!
Cation → Cathode (-ve) → Reduction
Cu2+
, Br-
+ H+
, OH-
(from water)
+
+
+
+
+
+
-
-
-
-
-
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
Al3+
+ 3e- AI -1.66↔
Mn2+
+ 2e- Mn -1.19↔
2H2O +2e- H↔ 2 + 2OH-
-0.83
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
Cu+
+ e- ↔ Cu +0.52
I2 + 2e- ↔ 2I-
+0.54
Fe3+
+ e- ↔ Fe2+
+0.77
1/2Br2 + e- ↔ Br-
+1.07
O2 + 4H+
+4e- ↔ H2O +1.23
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
1/2F2 + e- ↔ F-
+2.87
Discharged Br-
ion Br2 Discharged Cu2+
ion to Cu
О
Cu2+
/H+
Br-
/OH-
Eθ
= -ve → supply +0.73 v to breakdown CuBr2 Cu→ + Br2
Electrolysis (Aqueous Salt)
Factor affecting ion discharged
(Selective Discharge)
↓
- Molten/aqueous
- Relative E values of ion
- Conc ion – conc/diluted
- Nature of electrode
Reduction
Eθ
> more +ve easier gain e
2H+
+ 2e H↔ 2 Eθ
= -0.83
2H2O +2e- H↔ 2 + 2OH-
Eθ
= -0.83
Cu2+
+ 2e Cu E↔ θ
= +0.34
О
Oxidation
Eθ
> more +ve easier to lose e
2Br-
Br↔ 2 + 2e Eθ
= -1.07
4OH-
2H↔ 2O + O2 + 4e Eθ
= -1.23
2H2O 4H↔ +
+ O2 + 4e Eθ
= -1.23
Inert electrode
Carbon/graphite
Br-
Br-
OH-
OH-
Cu2+
Cu2+
H+
H+

12. Discharge of ions
2 Cation + 2 Anion
Oxidation ← Anode (+ve) ← Anion
KI aqueous Electrolytic Cell
2H+
+ 2e H↔ 2 Eθ
= -0.83
2I-
I↔ 2 + 2e Eθ
= -0.54
KI H→ 2+ Br2 Eθ
= -1.37V
Eθ
= -1.37V
-ve (NON spontaneous)
Conversion electrical to chemical energy
Energy needed to decompose compound!!!!!!!!
Cation → Cathode (-ve) → Reduction
K+
, I-
+ H+
, OH-
(from water)
+
+
+
+
+
+
-
-
-
-
-
Oxidized sp ↔ Reduced sp Eθ
/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI -1.66↔
Mn2+
+ 2e- Mn -1.19↔
2H2O +2e- H↔ 2 + 2OH-
-0.83
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
I2 + 2e- ↔ 2I-
+0.54
Fe3+
+ e- ↔ Fe2+
+0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
O2 + 4H+
+4e- ↔ H2O +1.23
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
1/2F2 + e- ↔ F-
+2.87
Discharged I-
ion I2 Discharged H+
ion to H2
О
K+
/H+
I-
/OH-
Eθ
= -ve → supply +1.37 v to breakdown KI H→ 2 + I2
Electrolysis (Aqueous Salt)
Factor affecting ion discharged
(Selective Discharge)
↓
- Molten/aqueous
- Relative E values of ion
- Conc ion – conc/diluted
- Nature of electrode
Reduction
Eθ
> more +ve easier gain e
K+
+ e K E↔ θ
= -2.93
2H+
+ 2e H↔ 2 Eθ
= -0.83
2H2O +2e- H↔ 2 + 2OH-
Eθ
= -0.83
О
Oxidation
Eθ
> more +ve easier to lose e
2I-
I↔ 2 + 2e Eθ
= -0.54
4OH-
2H↔ 2O + O2 + 4e Eθ
= -1.23
2H2O 4H↔ +
+ O2 + 4e Eθ
= -1.23
ОО
Inert electrode
Carbon/graphite
OH-
OH-
I -
I -
H+
H+
K+
K+

13. Discharge of ions
2 Cation + 2 Anion
Oxidation ← Anode (+ve) ← Anion
K2SO4 aqueous Electrolytic Cell
2H+
+ 2e H↔ 2 Eθ
= -0.83
4OH-
2H↔ 2O+ O2 + 4e Eθ
= -1.23
K2SO4 H→ 2+ O2 Eθ
= -2.06V
Eθ
= -2.06V
-ve (NON spontaneous)
Conversion electrical to chemical energy
Energy needed to decompose compound!!!!!!!!
Cation → Cathode (-ve) → Reduction
K+
, SO4
2-
+ H+
, OH-
(from water)
+
+
+
+
+
+
-
-
-
-
-
Oxidized sp ↔ Reduced sp Eθ/V
Li+
+ e- Li↔ -3.04
K+
+ e- K↔ -2.93
Na+
+ e- Na↔ -2.71
Mg2+
+ 2e- Mg↔ -2.37
Al3+
+ 3e- AI -1.66↔
Mn2+
+ 2e- Mn -1.19↔
2H2O +2e- H↔ 2 + 2OH-
-0.83
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
I2 + 2e- ↔ 2I-
+0.54
Fe3+
+ e- ↔ Fe2+
+0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
O2 + 4H+
+4e- ↔ H2O +1.23
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
S2 O8
2-
+ 2e ↔ SO4
2-
+2.01
-
Discharged OH-
ion O2 Discharged H+
ion to H2
О
K+
/H+
SO4
2-
/OH-
Eθ
= -ve → supply +2.06 v to breakdown K2SO4 H→ 2 + O2
Electrolysis (Aqueous Salt)
Factor affecting ion discharged
(Selective Discharge)
↓
- Molten/aqueous
- Relative E values of ion
- Conc ion – conc/diluted
- Nature of electrode
Reduction
Eθ
> more +ve easier gain e
K+
+ e K E↔ θ
= -2.93
2H+
+ 2e H↔ 2 Eθ
= -0.83
2H2O +2e- H↔ 2 + 2OH-
Eθ
= -0.83
О
Oxidation
Eθ
> more +ve easier to lose e
4OH-
2H↔ 2O + O2 + 4e Eθ
= -1.23
2H2O 4H↔ +
+ O2 + 4e Eθ
= -1.23
2SO4
2-
S↔ 2O8
2-
+ 2e Eθ
= -2.01
ОО
H2 gas
Ratio 1:2
O2 gas
Inert electrode
Carbon/graphite
OH-
OH-
SO4
2-
SO4
2-
K+
K+
H+
H+

14. Discharge of ions
2 Cation + 2 Anion
Oxidation ← Anode (+ve) ← Anion
AgNO3 aqueous Electrolytic Cell
Ag+
+ e Ag E↔ θ
= +0.80
4OH-
2H↔ 2O+ O2 + 4e Eθ
= -1.23
AgNO3 Ag + O→ 2 Eθ
= -0.43V
Eθ
= -0.43V
-ve (NON spontaneous)
Conversion electrical to chemical energy
Energy needed to decompose compound!!!!!!!!
Cation → Cathode (-ve) → Reduction
Ag+
, NO3
-
+ H+
, OH-
(from water)
+
+
+
+
+
+
-
-
-
-
-
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↔
2H2O +2e- H↔ 2 + 2OH-
-0.83
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
I2 + 2e- ↔ 2I-
+0.54
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
O2 + 4H+
+4e- ↔ H2O +1.23
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
S2 O8
2-
+ 2e ↔ SO4
2-
+2.01
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
Discharged OH-
ion O2 Discharged Ag+
ion to Ag
О
Ag+
/H+
NO3
-
/OH-
Eθ
= -ve → supply +0.43 v to breakdown AgNO3 Ag + O→ 2
Electrolysis (Aqueous Salt)
Factor affecting ion discharged
(Selective Discharge)
↓
- Molten/aqueous
- Relative E values of ion
- Conc ion – conc/diluted
- Nature of electrode
Reduction
Eθ
> more +ve easier gain e
2H+
+ 2e H↔ 2 Eθ
= -0.83
2H2O +2e- H↔ 2 + 2OH-
Eθ
= -0.83
Ag+
+ e Ag E↔ θ
= +0.80
О
Oxidation
Eθ
> more +ve easier to lose e
4OH-
2H↔ 2O + O2 + 4e Eθ
= -1.23
2H2O 4H↔ +
+ O2 + 4e Eθ
= -1.23
NO3
-
cannot be discharged
Inert electrode
Carbon/graphite
OH-
OH-
NO3
-
NO3
-
H+
H+
Ag+
Ag+

15. Discharge of ions
1 Cation + 2 Anion
Oxidation ← Anode (+ve) ← Anion
H2SO4 aqueous Electrolytic Cell
2H+
+ 2e H↔ 2 Eθ
= -0.83
4OH -
2H↔ 2O + O2 + 4e Eθ
= -1.23
2H2O 2H→ 2 + O2 Eθ
= -2.06V
Eθ
= -2.06V
-ve (NON spontaneous)
Conversion electrical to chemical energy
Energy needed to decompose compound!!!!!!!!
Cation → Cathode (-ve) → Reduction
H+
, SO4
2-
+ H+
, OH-
(from water)
+
+
+
+
+
+
-
-
-
-
-
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↔
2H2O +2e- H↔ 2 + 2OH-
-0.83
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
O2 + 4H+
+4e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+1.33
1/2CI2 + e- ↔ CI-
+1.36
S2 O8
2-
+ 2e ↔ SO4
2-
+2.01
1/2F + e- ↔ F-
+2.87
Discharged OH-
ion O2 gas Discharged H+
ion to H2 gas
О
О
H+
SO4
2-
/OH-
Eθ
=-ve → supply +2.06v to breakdown H2SO4 H→ 2 + O2
Electrolysis (Aqueous Salt)
Factor affecting ion discharged
(Selective Discharge)
↓
- Molten/aqueous
- Relative E values of ion
- Conc ion – conc/diluted
- Nature of electrode
Reduction
Eθ
> more +ve easier gain e
2H+
+ 2e H↔ 2 Eθ
= -0.83
2H2O +2e- H↔ 2 + 2OH-
Eθ
= -0.83
Oxidation
Eθ
> more +ve easier to lose e
4OH-
2H↔ 2O + O2 + 4e Eθ
= -1.23
2H2O 4H↔ +
+ O2 + 4e Eθ
= -1.23
2SO4
2-
S↔ 2O8
2-
+ 2e Eθ
= -2.01
О
H2 gas
O2 gas
Ratio 1:2
Inert electrode
Carbon/graphite
OH-
OH-
SO4
2-
SO4
2-
H+
H+
H+
H+

16. Discharge of ions
2 Cation + 2 Anion
Oxidation ← Anode (+ve) ← Anion
Conc NaCI Electrolytic Cell
2H+
+ 2e H↔ 2 Eθ
= -0.83
2CI -
CI↔ 2 + 2e Eθ
= -1.36
NaCI 2H→ 2 + CI2 + NaOH Eθ
= -2.19
Cation → Cathode (-ve) → Reduction
Na+
, CI-
+ H+
, OH-
(from water)
+
+
+
+
+
+
-
-
-
-
-
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
Al3+
+ 3e- AI -1.66↔
Mn2+
+ 2e- Mn -1.19↔
2H2O +2e- H↔ 2 + 2OH-
-0.83
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
O2 + 4H+
+4e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+1.33
1/2CI2 + e- ↔ CI-
+1.36
1/2F2 + e- ↔ F-
+2.87
Discharged CI-
ion CI2 gas Discharged H+
ion to H2 gas
О
О
Na+
/H+
CI-
/OH-
Inert electrode
Carbon/graphite
Eθ
=-ve → supply +2.19v to breakdown NaCI H→ 2 + CI2 + NaOH
Electrolysis (Concentrated Salt)
Factor affecting ion discharged
(Selective Discharge)
↓
- Molten/aqueous
- Relative E values of ion
- Conc ion – conc/diluted
- Nature of electrode
Reduction
Eθ
> more +ve easier gain e
Na+
+ e Na E↔ θ
= -2.71
2H+
+ 2e H↔ 2 Eθ
= -0.83
2H2O +2e- H↔ 2 + 2OH-
Eθ
= -0.83
О
Oxidation
Eθ
> more +ve easier to lose e
4OH-
2H↔ 2O + O2 + 4e Eθ
= -1.23
2H2O 4H↔ +
+ O2 + 4e Eθ
= -1.23
2CI-
CI↔ 2 + 2e Eθ
= -1.36
О
Ratio 1:2
H2 gas
CI2 gas
Dilute NaCI – OH-
discharged due to Eθ
value
Conc NaCI – CI-
discharged due to overpotential factor
Discharged of H+
and OH-
ion need addition voltage
due to high activation energy for H2/O2 production
If Conc CI-
is high ↑ – it is preferred !!!!!!
OH-
OH-
CI -
CI -
H+
H+
Na+
Na+

17. Discharge of ions
2 Cation + 2 Anion
Oxidation ← Anode (+ve) ← Anion
Conc CuCI2 Electrolytic Cell
Cu2+
+ 2e Cu↔ Eθ
= +0.34
2CI-
CI↔ 2 + 2e Eθ
= -1.36
CuCI2 Cu + O→ 2 Eθ
= -0.89V
Cation → Cathode (-ve) → Reduction
Cu2+
, CI-
+ H+
, OH-
(from water)
+
+
+
+
+
+
-
-
-
-
-
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
Al3+
+ 3e- AI -1.66↔
Mn2+
+ 2e- Mn -1.19↔
2H2O +2e- H↔ 2 + 2OH-
-0.83
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
Cu+
+ e- ↔ Cu +0.52
I2 + 2e- ↔ 2I-
+0.54
Fe3+
+ e- ↔ Fe2+
+0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
O2 + 4H+
+4e- ↔ H2O +1.23
1/2CI2 + e- ↔ CI-
+1.36
1/2F2 + e- ↔ F-
+2.87
Discharged CI-
ion CI2 Discharged Cu2+
ion to Cu metal
О
Cu2+
/H+
CI-
/OH-
Eθ
= -ve → supply +0.89 v to breakdown CuCI2 Cu→ + O2
Factor affecting ion discharged
(Selective Discharge)
↓
- Molten/aqueous
- Relative E values of ion
- Conc ion – conc/diluted
- Nature of electrode
Reduction
Eθ
> more +ve easier gain e
2H+
+ 2e H↔ 2 Eθ
= -0.83
2H2O +2e- H↔ 2 + 2OH-
Eθ
= -0.83
Cu2+
+ 2e Cu E↔ θ
= +0.34
О
Oxidation
Eθ
> more +ve easier to lose e
4OH-
2H↔ 2O + O2 + 4e Eθ
= -1.23
2H2O 4H↔ +
+ O2 + 4e Eθ
= -1.23
2CI-
CI↔ 2 + 2e Eθ
= -1.36
ОО
Inert electrode
Carbon/graphite
Electrolysis (Concentrated Salt)
Dilute CuCI2 – OH-
discharged due to Eθ
value
Conc CuCI2 – CI-
discharged due to overpotential factor
Discharged of H+
and OH-
ion need addition voltage
due to high activation energy for H2/O2 production
If Conc CI-
is high ↑ – it is preferred !!!!!!
CI2 gas
copper
OH -
OH -
CI -
CI -
Cu2+
Cu2+
H+
H+

18. Carbon electrode
Discharge of ions
2 Cation 2 Anion
Oxidation ← Anode (+ve) ← Anion
CuCI2 aqueous Electrolytic Cell
Cation → Cathode (-ve) → Reduction
Cu2+
, CI-
+ H+
, OH-
(from water)
+
+
+
+
+
+
-
-
-
-
-
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
Al3+
+ 3e- AI -1.66↔
Mn2+
+ 2e- Mn -1.19↔
2H2O +2e- H↔ 2 + 2OH-
-0.83
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
Cu+
+ e- ↔ Cu +0.52
I2 + 2e- ↔ 2I-
+0.54
Fe3+
+ e- ↔ Fe2+
+0.77
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
O2 + 4H+
+4e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+1.33
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
1/2F2 + e- ↔ F-
+2.87
Discharged Cu2+
ion to Cu metal
О
CI-
/OH-
Electrolysis (Aqueous Salt)
Factor affecting ion discharged
(Selective Discharge)
↓
- Molten/aqueous
- Relative E values of ion
- Conc ion – conc/diluted
- Nature of electrode
Reduction
Eθ
> more +ve easier gain e
2H+
+ 2e H↔ 2 Eθ
= -0.83
2H2O +2e- H↔ 2 + 2OH-
Eθ
= -0.83
Cu2+
+ 2e Cu E↔ θ
= +0.34
О
Copper electrode
as anode
Cu easier discharge
↓
due nature electrode
↓
Cu → Cu2+
+ 2e
↓
Cu electrode dissolve
Copper electrode
OH-
discharged
↓
due to Eθ
value
↓
4OH-
2H↔ 2O+O2 + 4e
↓
O2 gas
+
+
+
+
+
Cu → Cu2+
+ 2e
copper
electrode
Cu → 2e + Cu2+
Cu2+
Cu2+
Cu2+
Cu2+
Cu → 2e + Cu2+
Cu → 2e + Cu2+
Cu2+
Cu2+
e-
e-
e e
e- e- e -
At Anode
Copper electrode oxidizes/dissolve
Conc copper ions unchanged
Mass of Cu anode decreased
Mass of Cu cathode increased
Cu2+
Cu2+
Cu2+
OH-
OH-
CI -
CI -
H+
H+
Cu2+
Cu2+
Cu2+
/H+

19. AgNO3 aqueous Electrolytic Cell
Carbon electrode
Discharge of ions
2 Anion
Oxidation ← Anode (+ve) ← Anion Cation → Cathode (-ve) → Reduction
Ag+
, NO3
-
+ H+
, OH-
(from water)
+
+
+
+
+
+
-
-
-
-
-
NO3
-
/OH-
Electrolysis (Aqueous Salt)
Factor affecting ion discharged
(Selective Discharge)
↓
- Molten/aqueous
- Relative E values of ion
- Conc ion – conc/diluted
- Nature of electrode
Reduction
Eθ
> more +ve easier gain e
2H+
+ 2e H↔ 2 Eθ
= -0.83
2H2O +2e- H↔ 2 + 2OH-
Eθ
= -0.83
Ag+
+ e Ag E↔ θ
= +0.80
Copper electrode
as anode
Ag easier discharge
↓
due nature electrode
↓
Ag → Ag+
+ e
↓
Ag electrode dissolve
Silver electrode
OH-
discharged
↓
due to Eθ
value
↓
4OH-
2H↔ 2O+O2 + 4e
↓
O2 gas
+
+
+
+
+
Ag → Ag+
+ e
silver
electrode
Ag → e + Ag+
Ag+
Ag+
Ag+
Ag+
Ag → e + Ag+
Ag → e + Ag+
Ag+
Ag+
e-
e-
e e
e- e- e -
At Anode
Silver electrode oxidizes/dissolve
Conc silver ions unchanged
Mass of Ag anode decreased
Mass of Ag cathode increased
Ag+
Ag+
Ag+
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↔
2H2O +2e- H↔ 2 + 2OH-
-0.83
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
I2 + 2e- ↔ 2I-
+0.54
Ag+
+ e- ↔ Ag +0.80
1/2Br2 + e- ↔ Br-
+1.07
O2 + 4H+
+4e- ↔ H2O +1.23
Cr2O7
2-
+14H+
+6e- ↔ 2Cr3+
+1.33
1/2CI2 + e- ↔ CI-
+1.36
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
S2 O8
2-
+ 2e ↔ SO4
2-
+2.01
MnO4
-
+ 8H+
+ 5e- ↔ Mn2+
+ 4H2O +1.51
ОО
Discharged Ag+
ion to Ag
-
-
-
-
-
OH -
OH -
NO3
-
NO3
-
Ag+
Ag+
H+
H+
Ag+
/H+

20. Electrolyte Electrode Ions Cathode (-) Anode (+)
PbBr2 (molten) Carbon Pb2+
/ Br-
Pb2+
+ 2e Pb→
Pb
2Br-
Br→ 2 + 2e
Br2
CaCI2 (molten) Carbon Ca2+
/CI-
Ca2+
+2e Ca→
Ca
2CI-
CI→ 2 + 2e
CI2
NaCI Carbon Na+
/ CI –
H+
/OH-
2H+
+ 2e H→ 2
H2
4OH-
2H↔ 2O +O2 + 4e
O2
NaCI
(conc)
Carbon Na+
/ CI–
H+
/OH-
2H+
+ 2e H→ 2
H2
2CI-
CI→ 2 + 2e
CI2
NaI Carbon Na+
/ I–
H+
/OH-
2H+
+ 2e H→ 2
H2
2I-
I→ 2 + 2e
I2
CuCI2 Carbon Cu2+
/ CI–
H+
/OH-
2H+
+ 2e H→ 2
H2
4OH-
2H↔ 2O +O2 + 4e
O2
CuCI2
(conc)
Carbon Cu2+
/CI-
H+
/OH -
2H+
+ 2e H→ 2
H2
2CI-
CI→ 2 + 2e
CI2
CuCI2 Copper Cu2+
/CI-
Cu2+
+2e Cu→
Cu
Cu Cu→ 2+
+ 2e
Cu
CuBr2 Carbon Cu2+
/Br-
H+
/OH -
2H+
+ 2e H→ 2
H2
2Br-
Br→ 2 + 2e
Br2
KI Carbon K+
/I-
H+
/OH -
2H+
+ 2e H→ 2
H2
2I-
I→ 2 + 2e
I2
AgNO3 Carbon Ag+
/NO3
-
H+
/OH -
Ag+
+ e Ag→
Ag
4OH-
2H↔ 2O +O2 + 4e
O2
AgNO3 Silver Ag+
/NO3
- Ag+
+ e Ag→ Ag Ag→ +
+ e
K2SO4 Carbon K+
/SO4
2-
H+
/OH -
2H+
+ 2e H→ 2
H2
4OH-
2H↔ 2O +O2 + 4e
O2
H2SO4 Carbon H+
/SO4
2-
H+
/OH -
2H+
+ 2e H→ 2
H2
4OH-
2H↔ 2O +O2 + 4e
O2
HCI Carbon H+
/CI-
H+
/OH -
2H+
+ 2e H→ 2
H2
4OH-
2H↔ 2O +O2 + 4e
O2
+ - + -
Ease Anion discharged
NO3
–
SO4
2-
CI–
Br–
I–
OH–
Ease Cation discharged
K+
Ca2+
Na+
Mg2+
Al 3+
Zn2+
Fe2+
Sn2+
Pb2+
H+
Cu2+
Ag+
easier
easier
Electrolytic cell
Conversion electrical to chemical energy
+ -
Anode (+ve)
Oxidation
Cathode (-ve)
Reduction
CathodeAnode
Factor affecting ion discharged
(Selective Discharge)
Relative E
values of ion
Conc ion
conc/diluted
Nature of
electrode
PANIC
Positive is Anode, Negative Is Cathode
NO3
–
- diff to discharge
- ON for N is +5 (very high)
- Diff to lose e to get higher

21. 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 - carry charge of – 1.6 x 10 -19
C
6.28 x 10 18
electron - carry charge of - 1 C 1A
6.02 x 10 23
electron (1 Mol) - carry charge of - 96500C 1F
Electric current
Flow electric charges (electron)
From High electric potential – low potential
ond
electron
ond
Coulomb
A
sec.1
.1028.6
sec1
1
1
18
×
==
Current
Flow of
charges
-
-
-
ItQ = t = Time/ s
Find amt charges pass through a sol if
Current is 2.ooA, time is 15 mins
ItQ =
Q = Amt Charges/ C
I = Current/ A
CQ 1800601500.2 =××=
Faraday’s constant (F) – charge on 1 mol of electron 96500 C mol-1
1
1923
965001
106.11002.6
−
−
=
×××=
×=
CmolF
CF
eLF
1A = 6.28 x 1018
e
1 second
L = Avogadro constant
1 Faraday – Quantity charge 96500C supply to 1 mol electron
Faraday's 1st Law Electrolysis Faraday's 2nd Law Electrolysis
Amt charges (Q)
Mass produce is directly proportional
to the quantity of electricity/charges ( C )
Factor affecting mass substance liberated
Charge on ion
Current Time
ItQ =
Mass produce is inversely proportional
to
charges on ion
Cu2+
+ 2e Cu↔Ag+
+ e Ag↔ AI3+
+ 3e AI↔
+1 +2 +3
1 mol e → 1 mol Ag 2 mol e → 1 mol Cu 3 mol e → 1 mol AI
Pass 1 mol e 1 mol e → 1 mol Ag 1 mol e → 1/2 mol Cu 1 mol e → 1/3 mol AI

22. 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 - carry charge of – 1.6 x 10 -19
C
6.28 x 10 18
electron - carry charge of - 1 C 1A
6.02 x 10 23
electron (1 Mol) - carry charge of - 96500C 1F
Electric current
Flow electric charges (electron)
From High electric potential – low potential
ond
electron
ond
Coulomb
A
sec.1
.1028.6
sec1
1
1
18
×
==
Current
Flow of
charges
-
-
-
ItQ = t = Time/ s
Find amt charges pass through a sol if
Current is 2.ooA, time is 15 mins
ItQ =
Q = Amt Charges/ C
I = Current/ A
CQ 1800601500.2 =××=
Faraday’s constant (F) – charge on 1 mol of electron 96500 C mol-1
1
1923
965001
106.11002.6
−
−
=
×××=
×=
CmolF
CF
eLF
1A = 6.28 x 1018
e
1 second
L = Avogadro constant
1 Faraday – Quantity charge 96500C supply to 1 mol electron
Copper (II) sulfate electrolyzed using current -- 0.150A for 5 hrs. Cal mass of Cu deposited
CQ
Q
ItQ
2700
60605150.0
=
×××=
=
Cu2+
+ 2e Cu↔
2 mol e → 1 mol Cu
0.028 mol e 0.014 mol Cu→
emolC
emolC
...028.0
96500
2700
2700
...196500
=→
→
Find Current/I → Find Charge/Q → Find mol electron → Find Mass deposited
use Faraday’s constant
Mass = mol x RAM
Mass = 0.014 x 63.5
Mass = 0.889 g
Mass deposited
(Cathode)
Cu
11
Cu2+
Cu2+

23. Electrolysis
AI
t
Q
I
ItQ
4.6
605.12
4787
=
×
==
=Cr3+
+ 3e Cr↔
1 mol Cr → 3 mol e
0.0165 mol Cr → 0.0495 mol e
Find Mass → Find mol electron → Find Charges/Q → Find current/I
use Faraday’s constant
Mass = mol x RAM
0.86 = mol x 52.00
mol = 0.0165
Electrolysis Cr2(SO4)3 yield 0.86g of Cr after passing current for 12.5 min. Find amt of current used.
1 mol e → 96500C
0.0495mol e 96500 x 0.0495→
= 4787 C
Find time /hrs need to produce 25g of Cr from Cr2(SO4)3 with current of 1.1A
Find Mass → Find mol electron → Find Charges/Q →Find current/I
Cr3+
+ 3e Cr↔ use Faraday’s constant
1 mol Cr → 3 mol e
0.48 mol Cr → 1.44 mol e
Mass = mol x RAM
25 = mol x 52.00
mol = 0.48
1 mol e → 96500C
1.44mol e 96500 x 1.44→
= 138960 C
1.35
1.1
138960
=
==
=
t
I
Q
t
ItQ
Mass deposited
(Cathode)
Cr3+
Cr3+
Cr
Find vol of H2 gas collect at cathode when aq sol Na2SO4 electrolyzed for 2.00 hours with a 10A.
Mass deposited
(Cathode)
Cr
Cr3+
Cr3+
Find Current/I → Find Charge/Q → Find mol electron → Find Vol
2H+
+ 2e H↔ 2
CQ
Q
ItQ
72000
6060200.2
=
×××=
=
use Faraday’s constant
emolC
emolC
...746.0
96500
72000
72000
...196500
=→
→
2 mol e → 1 mol H2
0.746 mol e 0.373 mol H→ 2
H2 O2
22
33
44
Vol = 8.35 dm3

24. Faraday's 1st Law Electrolysis
Faraday's 2nd Law Electrolysis
Amt charges (Q)
Mass produce is directly proportional
to the quantity of electricity/charges ( C )
Factor affecting mass substance liberated
Charge on ion
Current Time
ItQ =
Mass produce is inversely proportional to charges on ion
Cu2+
+ 2e Cu↔Ag+
+ e Ag↔ AI3+
+ 3e AI↔
+1 +2 +3
1 mol e → 1 mol Ag 2 mol e → 1 mol Cu 3 mol e → 1 mol AI
Pass 1 mol electron across
1 mol e → 1 mol Ag 1 mol e → 1/2 mol Cu 1 mol e → 1/3 mol AI
Ag+
Ag+
-
-
-
-
-
-
+
+
+
+
+
+ Cu2+
Cu2+
AI3+
AI3+
AgNO3,CuSO4, AICI3 connect in series. Same amt current used.
Cal mass Cu and Al when 10.8 g Ag deposited.
Ag+
+ e Ag↔
1 mol Ag → 1 mol e
0.1 mol Ag →0.1 mol e
Mass = mol x RAM
10.8 = mol x 108
mol = 0.1
Cu2+
+ 2e Cu↔
2 mol e → 1 mol Cu
0.1 mol e → 0.05 mol Cu
AI3+
+ 3e AI↔
3 mol e → 1 mol AI
0.1 mol e → 0.03 mol AI
Mass Cu = 0.05 mol Mass AI = 0.03 mol
AgNO3, H3SO4 connect in series. Same amt current used
Cal vol H2,O2 when 10.8 g Ag deposited.
-
-
Ag+
Ag+
O2
H2
Ag+
+ e Ag↔
1 mol Ag → 1 mol e
0.1 mol Ag → 0.1 mol e
Mass = mol x RAM
10.8 = mol x 108
mol = 0.1
2H+
+ 2e H↔ 2
2 mol e → 1 mol H2
0.1 mol e 0.05 mol H→ 2
4OH-
2H↔ 2O +O2 + 4e
4 mol e → 1 mol O2
0.1 mol e 0.025 mol O→ 2
2.24 dm3
0.56 dm3

25. Faraday's 1st Law Electrolysis Faraday's 2nd Law Electrolysis
Amt charges (Q)
Mass produce is directly proportional
to the quantity of electricity/charges ( C )
Factor affecting mass substance liberated
Charge on ion
Current Time
ItQ =
Mass produce is inversely proportional to charges on ion
Cu2+
+ 2e Cu↔Ag+
+ e Ag↔ AI3+
+ 3e AI↔
+1 +2 +3
1 mol e → 1 mol Ag 2 mol e → 1 mol Cu 3 mol e → 1 mol AI
Pass 1 mol electron across
1 mol e → 1 mol Ag 1 mol e → 1/2 mol Cu 1 mol e → 1/3 mol AI
Purification of metal
Application of Electrolysis
Extraction reactive metal
Aluminium Sodium
- ve
electrode
Aluminium
metal
AI2O3
Al3+
+ 3e → Al
Electroplating
- Prevent corrosion
- Improve appearance
Copper, chromium, silver
- ve
Sodium
metal
Na+
+ e → Na
NaCI + ve
-
-
-
-
-
-
-
-
+
+
+
+
+
+
+
+
+
+
+
+
-
-
-
-
Anode (+ve)
Plating metal
Cathode (-ve)
Object
+
+
-
-
Anode (+ve)
Impure Cu metal
Mass decrease
Cathode (-ve)
Pure Cu metal
Mass increase
Cu2+
+ 2e Cu↔
Cu2+
Cu2+
Cu2+
Cu Cu↔ 2+
+ 2e
2CI-
-2e → CI2

26. Electrolysis of KI
Electrolysis of waterExcellent Silver crystal formation
Galvanizing Iron with Zinc
PANIC
Positive is Anode, Negative Is Cathode
Factor affecting ion discharged
(Selective Discharge)
Relative E
values of ion
Conc ion
conc/diluted
Nature of
electrode
Ease Cation discharged
K+
Ca2+
Na+
Mg2+
Al 3+
Zn2+
Fe2+
Sn2+
Pb2+
H+
Cu2+
Ag+ easier
Ease Anion discharged
NO3
–
SO4
2-
CI–
Br–
I–
OH–
easier
NO3
–
- diff to discharge
- ON for N is +5 (very high)
- Diff to lose e to get higher
Anode (+ve)
Oxidation
Cathode (-ve)
Reduction
Conversion electrical to chemical energy
Electrolytic cell
+ -
Faraday's 1st Law Electrolysis
Mass produce is directly proportional
to the quantity of electricity/charges ( C )
Factor affecting mass substance liberated
Amt charges (Q)
Charge on ion
Current Time
ItQ =
Faraday's 2nd Law Electrolysis
Mass produce is inversely proportional
to charges on ion
+1 +2
Ag+
+ e Ag↔ Cu2+
+ 2e Cu↔
1 mol e → 1 mol Ag 2 mol e → 1 mol Cu
1 mol e → 1 mol Ag 1 mol e → 1/2 mol Cu
Pass 1 mol electron across

27. 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
Prepared by Lawrence Kok
Check out more video tutorials from my site and hope you enjoy this tutorial
http://lawrencekok.blogspot.com