# Is precipitation always involved in a double displacement reaction?

Jun 9, 2018

Not necessarily.

#### Explanation:

There are a variety of spontaneous double displacement reactions. Some but not all of them involve the production of a precipitate.

For example, the neutralization reaction between hydrochloric acid $\text{HCl}$ and sodium hydroxide $\text{NaOH}$ counts as a double displacement reaction. However, this reaction produces no precipitate.

$\text{NaOH" (aq) + "HCl" (aq) color(navy)(to) "NaCl" (aq) + "H"_2"O} \textcolor{p u r p \le}{\left(l\right)}$

Neutralization reactions are feasible as double displacement reaction thanks to the production of water $\text{H"_2"O}$, a weak electrolyte that barely disassociate on its own. Meaning that as the reaction proceeds, the formation of water would act like a ${\text{H}}^{+}$ / ${\text{OH}}^{-}$ sink that continuously removes the two ions from the system.

Other types of reactions, such as those involving the evolution of a gas e.g., ${\text{CO}}_{2}$ or ${\text{NH}}_{3}$ can also be spontaneous. Here's a list of them on the English Wikipedia.