What is double decomposition?
What is the difference between decomposition and double decomposition?

Asked by ROLLY ALEX | 23rd Nov, 2017, 10:31: PM

Expert Answer:

Double decomposition: A type of chemical change in which two compounds in a solution react to form two new compounds by the mutual exchange of radicals. Usually, a solid is formed as a result of the reaction.

These reactions are of two types:

Precipitation reactions and Neutralisation reactions.

Precipitation reactions

The insoluble solid formed during the double displacement reactions is called a precipitate. Reactions in which a precipitate is formed as one of the products are also called precipitation reactions.

Sodium sulphate reacts with barium chloride to form barium sulphate and sodium chloride solution.    

                Na2SO4 (aq)   +   BaCl2           BaSO4(s)    +      2NaCl(aq)

                Sodium            Barium                Barium              Sodium

               sulphate           chloride             sulphate             chloride

Neutralisation reactions

The reaction between an acid and a base to form a salt and water is called as neutralisation reaction.


                  NaOH(aq)   +    HCl(aq)                NaCl(aq)   +    H2O(l)

                 Sodium        Hydrochloric                 Sodium         Water

               hydroxide           acid                        chloride          


Decomposition reaction

A chemical reaction in which a single compound splits into two or more simple substances is called a decomposition reaction.

When the mercuric oxide is heated in a crucible, the orange-red powder begins to darken and a silver mirror begins to deposit on the cooler parts of the crucible. This is mercury. If we hold a glowing splint near the crucible, it can relight. This shows that the gas evolved during the reaction is oxygen.

2HgO(s)                               2Hg(s)     +    O2

Mercuric oxide                   Mercury     Oxygen

The difference between decomposition and double decomposition reaction is in decomposition reaction there is only one reactant and in double decomposition reaction, there are two reactants.

Answered by Ramandeep | 24th Nov, 2017, 10:20: AM