Question

What is a double decomposition reaction? Give an example each for neutralization and precipitation reactions.

Answer 1

Step-I Double decomposition reaction:-

Double decomposition reactions are those in which two compounds in a solution react to form two new compounds by mutual exchange of radicals. This type of reaction is also known as a double displacement reaction.

General reaction: $\mathrm{AB}+\mathrm{CD}\to \mathrm{AD}+\mathrm{CD}$

For Example:- $$\begin{gathered} \mathrm{HCl}(\mathrm{aq}.)+\mathrm{NaOH}(\mathrm{aq}.)\to \mathrm{NaCl}(\mathrm{aq}.)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \\ \left(\mathrm{Hydrochloric}\right)(\mathrm{Sodium}\mathrm{hydroxide})(\mathrm{Sodium}\mathrm{chloride})\left(\mathrm{Water}\right) \end{gathered}$$

Step-II: Neutralization reaction:-

When acid or base reacts to form a neutral salt solution, the reaction is called neutralization.

For Example:- When hydrochloric acid is reacting with sodium hydroxide then it will form sodium chloride(salt).

$$\begin{gathered} \mathrm{HCl}\left(\mathrm{aq}\right)+\mathrm{NaOH}\left(\mathrm{aq}\right)\to \mathrm{NaCl}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \\ (\mathrm{hydrochloric}(\mathrm{sodium}(\mathrm{sodium}(\mathrm{water}) \\ \mathrm{acid})\mathrm{hydroxide})\mathrm{chloride}) \end{gathered}$$

Step-III: Precipitation reaction:- Precipitation reactions are usually double displacement reactions involving the production of a solid form residue called the precipitate.

For Example:- When potassium hydroxide is reacting with calcium chloride then calcium hydroxide and potassium chloride will be formed.

$$\begin{gathered} 2\mathrm{KOH}(\mathrm{aq}.)+{\mathrm{CaCl}}_2(\mathrm{aq}.)\to \mathrm{Ca}{\left(\mathrm{OH}\right)}_2(\mathrm{aq}.)+2\mathrm{KCl}(\mathrm{aq}.) \\ (\mathrm{Potassium}(\mathrm{Calcium}(\mathrm{Calcium}(\mathrm{potassium} \\ \mathrm{hydroxide})\mathrm{chloride})\mathrm{hydroxide})\mathrm{chloride}) \end{gathered}$$