# Ionization Of Acids And Bases

Ionization of Acids and Bases

#### What is Ionization?

Ionization of a compound refers to a process in which a neutral molecule splits into charged ions when exposed in a solution.

According to Arrhenius theory, acids are the compounds that dissociate in aqueous medium to generate hydrogen ions, $H^+$ (aq). On the other hand, bases are the compounds which furnish hydroxyl ions, $OH^{-}$(aq) in aqueous medium.

Arrhenius theory plays an important role in explaining the ionization of acids and bases as mostly ionization takes place in aqueous medium. On the basis of degree of ionization of acids and bases, we can determine the strength of acids and bases. The degree of ionization differs for different acidic and basic compounds. Some acids such as perchloric acid ($HClO_4$), hydrochloric acid ($HCl$) dissociate completely into their constituent ions in aqueous medium. These acids are termed as strong acids. Ionization of acids yields hydrogen ions, thus these compounds act as proton donors. Similarly, some bases like lithium hydroxide ($LiOH$), sodium hydroxide ($NaOH$) too completely dissociate into their ions in an aqueous medium. These bases are termed as strong bases. Ionization of these bases yields hydroxyl ions, ($OH^-$).

Hence, the degree of ionization of acids and bases depends on the degree of dissociation of compounds into their constituent ions. Strong acids and bases have high degree of ionization in comparison to weak acids and bases. Also, a strong acid implies good proton donor whereas strong base implies good proton acceptor. For example: dissociation of weak acid HA

$HA ~(aq)~ + ~H_2O~ (l)~ ⇌~H_3O^+~(aq)~ + ~A^-~ (aq)$

## Explanation

This reaction implies that acid dissociation equilibrium is dynamic in nature where transfer of proton can take place in both forward and backward direction. If $HA$ has a higher tendency to donate proton in comparison to $H_3O^+$, $HA$ acts as a strong acid in comparison to $H_3O^+$.. Since, the stronger acid donates proton to the stronger base. The equilibrium moves in the direction of formation of weaker acid and weaker base. The strong acids generally have weaker conjugate base whereas strong bases have weaker conjugate acids. This is because of high degree of ionization of strong acids and bases.

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