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Why Are Decomposition Reactions Called the Opposite of Combination Reactions? Write Equations for These Reactions - Science

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Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.

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Solution 1

Decomposition reactions are those in which a compound breaks down to form two or more substances. These reactions require a source of energy to proceed. Thus, they are the exact opposite of combination reactions in which two or more substances combine to give a new substance with the release of energy.For Example:
Decomposition Reaction:

CaCO3 (s) `""/Delta`>CaO(s)+CO2 (g)

Combination Reaction:
CaO (s) + H2O (l) → Ca(OH)2 (aq)

Solution 2

In decomposition reaction, a compound breaks down to two or more simple products, whereas in combination reaction, two or more reactants combine to form a single product. Therefore, both the reactions are opposite to each other.

For example, in a combination reaction, simple molecules of hydrogen and oxygen combine to form a water molecule.
 2H2 (g) + O2 (g) → 2H2(l)

While in decomposition reaction, reverse process takes place—​i.e., water decomposes to hydrogen and oxygen.
 2H2(l) → 2H2 (g) + O2 (g)

Concept: Types of Chemical Change or Chemical Reaction - Decomposition Reactions
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APPEARS IN

NCERT Class 10 Science
Chapter 1 Chemical Reactions and Equations
Q 11 | Page 15
Lakhmir Singh Class 10 Chemistry (Science)
Chapter 1 Chemical Reactions and Equations
Q 37.1 | Page 47
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