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CHEM 112 (100)
Lecture 1

CHEM 112 Lecture Notes - Lecture 1: Lithium Polymer Battery, Lithium-Ion Battery, Lead Dioxide


Department
Chemistry
Course Code
CHEM 112
Professor
John Carran
Lecture
1

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Batteries and Fuel Cells, Electrolysis
• Primary Cells (or batteries).
-Cell reaction is not reversible.
• Secondary Cells.
-Cell reaction can be reversed by passing electricity through the cell (charging).
• Flow Batteries and Fuel Cells.
-Materials pass through the battery which converts chemical energy to electric energy.
The Leclanché (dry) cell:
The Leclanché dry cell is the most common type of voltaic cell, invented by Georges Leclanché in
the 1860’s.
-It is called a dry cell because there is no free liquid present.
-It is cheap to produce, but as a primary cell, cannot be recharged.
-Oxidation: Zn(s) → Zn2+(aq) + 2 e
-Reduction: 2 MnO2 (s) + H2O(l) + 2 e - → Mn2O3 (s) + 2 OH- (aq)
-Acid-base reaction: NH4 + (aq) + OH- (aq) → NH3 (g) + H2O(l)
-Precipitation reaction: NH3 (g) + Zn2+(aq) + 2 Cl- (aq) → [Zn(NH3 )2 ]Cl2 (s)
- The NH3 (g) must be removed by complexing it to Zn2+ or it will adhere to the cathode, disrupting the
current
The Alkaline Cell
-Reduction: 2 MnO2 (s) + H2O(l) + 2 e - → Mn2O3 (s) + 2 OH- (aq)
-Oxidation reaction can be thought of taking place in two steps:
Zn(s) → Zn2+(aq) + 2 e –
Zn2+(aq) + 2 OH- (aq) → Zn(OH)2 (s)
---------------------------------------------------
Zn(s) + 2 OH- (aq) → Zn(OH)2 (s) + 2 e –
Eo cell = Eo (cathode) – Eo (anode)
= Eo (MnO2 /Mn2O3 ) – Eo (Zn(OH)2 /Zn)
= +0.118 V – (-1.246 V)
= +1.364 V
The Silver-Zinc Cell: A Button Battery
Zn(s), ZnO(s) | KOH(sat’d) | Ag2O(s), Ag(s)
Zn(s) + Ag2O(s) → ZnO(s) + 2 Ag(s) Ecell = 1.8 V
- Because no species in the overall reaction are in solution, there is very little electrolyte and the
batteries can be very small
The Nickel-Cadmium Cell: A Rechargeable Battery
2 NiO(OH)(s) + 2 H2O(l) + 2 e- → 2 Ni(OH)2 (s) + 2 OH- (aq)
Cd(s) + 2 OH- (aq) → Cd(OH)2 (s) + 2 e
Cd(s) + 2 NiO(OH)(s) + 2 H2O(l) → 2 Ni(OH)2 (s) + Cd(OH)2 (s)
- charging mode: Cd(s) is the cathode, NiO(OH)(s) is the anode
- decharging mode: NiO(OH)(s) is the cathode, Cd(s) is the anode
- Because they are going back and forth between anode and cathode, it is better to call the Cd(s)
electrode the negative electrode and the NiO(OH)(s) electrode the positive electrode
find more resources at oneclass.com
find more resources at oneclass.com
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