There are five basic types of chemical reactions: 1. Combination reactions involve simple substances combining to form more complex ones, such as hydrogen and oxygen forming water. 2. Decomposition reactions involve complex substances breaking down into simpler ones, such as water electrolysis producing hydrogen and oxygen. 3. Displacement reactions occur when a more reactive element displaces a less reactive one from its compound, such as zinc displacing hydrogen from hydrochloric acid. 4. Double displacement reactions involve the exchange of cations and anions between compounds forming new ionic compounds, like sodium chloride forming when sodium and chloride ions are exchanged. 5. Oxidation and reduction reactions occur simultaneously as other substances either gain or

1. Pranabjyoti Das
Tangla

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The transformation of chemical
substance into another chemical
substance is known as Chemical
Reaction. For example: rusting of iron,
setting of milk into curd, digestion of
food, respiration, etc.
In chemical reaction new substance is
formed which is completely different in
properties from the original substance,
so in a chemical reaction chemical
change takes place.

3. What is a Chemical Reaction ?
A chemical reaction is a process that leads to the
transformation of one set of chemical substances to
another with completely new properties.
For example:
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4. Types of Chemical reactions:
There are five basic types of chemical reactions. They are:
1. Combination reaction or Synthesis Reaction
2. Decomposition Reaction
3. Displacement Reaction or Replacement Reaction
4. Double displacement Reaction
5. Oxidation & Reduction Reactions or Redox Reactions
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6. In a synthesis or Combination reaction two or
more simple substances combine to form a more
complex substance.
These reactions are in the general form of
A + B = AB
One example of such a reaction is the
combination of Hydrogen and Oxygen to form
Water.
2H2 + O2 2H⇨ 2O
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7. One More example :
Sodium reacts with Chlorine to form Sodium Chloride
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10. When Water is electrolysed, it decomposes
to Hydrogen and Oxygen.
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For example: Zinc displaces Hydrogen
from Hydrochloric Acid as Hydrogen gas

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Double displacement reactions may be defined as the
chemical reactions in which one component each of
both the reacting molecules is exchanged to form the
products. During this reaction, the cations and anions
of two different compounds switch places, forming two
entirely different compounds.

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Double displacement reactions generally take
place in aqueous solutions in which the ions
precipitate and there is an exchange of ions.
For Example:

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CH4
(g) + 2 O2
(g) CO2
(g) + 2 H2
O(g)

16. Reduction Reactions
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Reduction is the loss of Oxygen or gain of Hydrogen

17. Redox Reactions Oxidation & Reduction Reactions
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Both Oxidation and Reduction reactions occur
simultaneously in the same chemical reaction. So,
Oxidation and Reduction reactions are studied
together and they are collectively called as Redox
Reactions

18. Watch a Video
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