# Why is neutralization a double replacement reaction?

Feb 8, 2014

An acid and and base neutralization involves an aqueous acid solution and an aqueous base solution combining in a double replacement reaction to form a salt and water.

The basic reaction for a double replacement react takes the following format:

$A B + C D \to C B + A D$

An example:

Nitric acid plus calcium hydroxide yield calcium nitrate and water

$2 H N {O}_{3}$ + $C a {\left(O H\right)}_{2}$ -------> $C a {\left(N {O}_{3}\right)}_{2}$ + $2 {H}_{2} O$

$H N {O}_{3}$ has a leading hydrogen, usually a tip off that this is an acid
$C a {\left(O H\right)}_{2}$ has a trailing hydroxide usually a tip off that this is a base

The positive ion $C {a}^{+} 2$ from the base joins the negative ion $N {O}_{3}$ from the acid to form the salt. $C a {\left(N {O}_{3}\right)}_{2}$

The ${H}^{+}$ from the acid joins the $O {H}^{-}$ from the base to form water ${H}_{2} O$

Since both partners in the reactants are changing to new partners in the products this is a double replacement reaction.

Always in a neutralization reaction the products are two neutral substance salt and water.

Another example

We will look at an example as Sulfuric Acid and Potassium Hydroxide neutralize each other in the following reaction:

${H}_{2} S {O}_{4} + 2 K O H \to {K}_{2} S {O}_{4} + 2 {H}_{2} O$

In a neutralization reaction between an acid and a base the typical outcome is a salt formed by the positive ion from the base and the negative ion from the acid. In this case the positive potassium ion (${K}^{+}$) and the polyatomic sulfate ($S {O}_{4}$) to for m the salt ${K}_{2} S {O}_{4}$.

The positive hydrogen (${H}^{+}$) from the acid and the negative hydroxide ion ($O {H}^{-}$) from the base form the water $H O H$ or ${H}_{2} O$.