Question

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

Why are decomposition reactions called the opposite of combination reactions? Explain with equations of these reactions.

Answer 1

Decomposition reactions occur when a compound breaks up into two or more simpler substances. On the other hand, combination reactions occur when two or more substances combine to form a single substance. Thus, decomposition reactions are the opposite of combination reactions.

Decomposition Reactions:

\[\ce{CaCO3_{(s)} -> CaO_{(s)} + CO2_{(g)}}\]

\[\ce{2H2O_{(l)} ->[Electricity] 2H2_{(g)} + O2_{(g)}}\]

Combination Reactions:

\[\ce{2H2_{(g)} + O2_{(g)} -> 2H2O_{(l)}}\]

\[\ce{NH3_{(g)} + HCl_{(g)} -> NH4Cl_{(s)}}\]