This document discusses electrochemical reactions and different types of cells. It defines electrochemical reactions as chemical reactions where electrical energy is consumed or produced. Examples of electrochemical reactions include electrolysis of copper sulfate, where copper sulfate decomposes with the absorption of electrical energy, and electroplating, where a thin metal coating is produced on another metal through an electrochemical process. The document also discusses different types of cells, such as dry cells, mercury cells, nickel-cadmium cells, and lithium-ion cells, which are used in various electronic devices.

1. Electrochemical Reactions

2. Electrolyte
•Substances which undergo chemical change
when electricity is passed through them.
Examples:
•Sodium chloride, copper sulphate, silver
nitrate etc.
•Acids, alkalis and salts in their molten form
as well as in aqueous solutions.

3. Electrode
The rods which are connected to the poles of the
battery and which transfer electricity to the
electrolyte.

6. Electrolysis

9. Observations:
• The color of copper sulphate solution fades.
• Deposition of copper at one electrode.
• In this reaction copper sulphate decomposed with the
absorption of electrical energy.
The process in which a substance undergoes
decomposition by the absorption of electrical
energy is known as electrolysis.

11. Observation:
• Electricity is produced as a result of a chemical
reaction between the acid and the metals kept
immersed in it.
Such arrangements which produce electricity as a
result of chemical reaction are known as
electrochemical cells.

13. Chemical reactions in which electrical energy
is consumed or produced are known as
electrochemical reactions.

14. Electroplating

15. Electricity is used to obtain a thin coating of a
particular metal on other metallic objects. This
process is called electroplating.
Electroplating is an electrochemical reaction.

16. Arrangement:
•Positive terminal of battery: Metal to be coated
•Negative terminal of battery :object on which
coating is to be made
•Electrolyte: salt solution of desired metal(In
case of silver and gold metal cyanide solution is
taken)
Example: Copper rod, metallic spoon, copper sulphate
solution

20. Forms of energy like heat, light and electricity are exchanged
during chemical reactions. There are chemical reactions which
involve the absorption or liberation of energy.
Chemical reactions in which energy is absorbed
are known as endoergic reactions and those in
which energy is liberated are known as exoergic
reactions.

21. • Reaction between magnesium and hydrochloric acid.
• Neutralization reaction between sodium hydroxide
and hydrochloric acid.
• Decomposition of potassium permanganate
• photosynthesis
• Decomposition of silver bromide
• Electrolysis of copper sulphate
• Electroplating
• Metals like zinc and copper react with acids

22. Different types of cells
Dry cell:
Used in radio, camera,clocks,toys

23. Mercury cell:
Used in watches, calculators, electronic instruments

24. Nickel-cadmium cell
Used in rechargeable torches, cameras

25. Lithium-ion cell
Used in mobile phone, laptop