# What is the difference between dilute HCl and liquid HCl?

Mar 31, 2017

One is a solution of a strong acid, the other is just a liquid (no acidic properties).

#### Explanation:

Liquified HCl has been cooled until the gas turns to a liquid, in the same way most other gases change on cooling. It is a pure substance in the liquid phase.

"Dilute" HCl implies you have dissolved a small amount of HCl gas into water. In this case, an ionization reaction occurs as follows:

$H C l \left(a q\right) + {H}_{2} O \rightarrow {H}_{3} {O}^{+} + C {l}^{-}$

This is a complete reaction (hence HCl is a strong acid), and the resulting hydronium ion, ${H}_{3} {O}^{+}$ gives the solution acidic properties.

Liquid HCl does not display these properties, as no reaction with ${H}_{2} O$ occurs.