Question

Explain the following type of chemical reaction, giving two examples for it:

Double displacement reaction

Answer 1

A chemical reaction in which two compounds in their aqueous state exchange their ions to form new compounds is called a double decomposition reaction.
Examples:

1. Calcium carbonate decomposes on strong heating to form two compounds, calcium oxide and carbon dioxide.
   \[\ce{CaCO3_{(s)}->[\Delta]CaO_{(s)} + CO2_{(g)}}\]
2. Mercuric oxide when heated decomposes to form mercury and oxygen.
   \[\ce{2HgO_{(s)}->[\Delta]2Hg_{(s)} + O2_{(g)}}\]