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






Two or more substances react to form a single product in a Combination Reaction .

A single reactant breaks down into more than one product in a Decomposition Reaction.

Usually, heat or energy is produced in such reactions.

Usually, heat or energy is used in such reactions.

General equation:

A + B  →  C

General equation:

A  →  B + C


CaO(s) + H 2 O(l) → Ca(OH) 2 (aq)


CaCO 3 (s)  →  CaO(s) + CO 2 (g)


In the above two reactions, since the mechanism is opposite , they are called opposite reactions. 

  1. Class 10
  2. Chapter 1 Class 10 - Chemical Reactions and Equations (Term 1)

About the Author

CA Maninder Singh's photo - Founder at Teachoo
CA Maninder Singh
CA Maninder Singh is a Chartered Accountant for the past 11 years and a teacher from the past 11 years. He teaches Science, Accounts and English at Teachoo