This document discusses batteries and electrochemistry. It defines a battery as two or more electrochemical cells connected in series to provide direct current. Batteries discussed include primary batteries that cannot be recharged and secondary batteries that can be recharged. Examples of primary batteries include dry cells and mercury cells, while secondary batteries include lead-acid and nickel-cadmium cells. The document focuses on the dry cell or Leclanché cell, describing its anode, cathode, and electrolyte components and the electrochemical reactions that occur.

1. Dr. K. RAJENDER REDDY
LECTURER IN CHEMISTRY
Email: raj3iict@gmail.com
24 April 2020 KRR-ELECTRO CHEMISTRY 1

2. Contents
• BATTERIES
1. Definition
2. A Battery to be practical use
3. Types of Batteries
4. Primary Battery, Examples
5. Secondary Battery, Examples
6. Dry Cell or Leclanche’s Cell
24 April 2020 KRR-ELECTRO CHEMISTRY 2

3. Battery
• Definition: Two or more electrochemical cells
connected in a series is called battery.
• Battery is used as a source of direct electric
current.
• Cell contains only one anode and cathode,
where as battery contains many anodes and
cathodes.
24 April 2020 KRR-ELECTRO CHEMISTRY 3

4. For a battery to be practical use
1. It should be light and compact
2. It’s voltage should not use vary appreciably
during its usage
3. It should have long life.
24 April 2020 KRR-ELECTRO CHEMISTRY 4

5. Types of batteries
• Batteries are two types
1. Primary batteries
2. Secondary batteries
24 April 2020 KRR-ELECTRO CHEMISTRY 5

6. Primary Battery or Primary Cell
• Definition: The cell in which the electrode
reactions can’t be reversed by passing an
external electrical energy is called primary
cell.
• i.e.: Non rechargeable batteries
• Ex: Dry cell, Mercury cell.
24 April 2020 KRR-ELECTRO CHEMISTRY 6

7. Secondary battery or Secondary cell
• Definition: The cell in which the electrode
reaction can be reversed by passing an
external electrical energy is called secondary
cell.
• i.e: Rechargeable batteries
• These are also called as storage cell
• Ex: Lead storage cell, Ni-Cd cell
24 April 2020 KRR-ELECTRO CHEMISTRY 7

8. Dry Cell or Leclanche’s cell (Video)
instruction: Double click on LOADING
24 April 2020 KRR-ELECTRO CHEMISTRY 8

9. Dry Cell or Leclanches Cell
• Anode : Zn (container)
• Cathode : Carbon rod(Graphite) immersed
in electrolyte.
• Electrolyte: Powder of ammonium chloride+
Zinc Chloride and Manganese dioxide in the
form of paste using starch and water.
24 April 2020 KRR-ELECTRO CHEMISTRY 9

10. Dry Cell or Leclanches Cell
• The reaction can be represented as:
• At anode: Zn Zn+2+2e-
• At cathode:
NH4
++MnO2+2e- MnO(OH)+NH3
• Over all reaction:
Zn +NH4
++MnO2 Zn+2 +MnO(OH)+NH3
24 April 2020 KRR-ELECTRO CHEMISTRY 10

11. THANK YOU
24 April 2020 KRR-ELECTRO CHEMISTRY 11