Question

Do acids dissociate or ionize?

Answer 1

Hint:Both the terms have almost similar meaning but still they are different and both the terms are used in terms of each other. To explain the solution we should first know how an acid behaves when it is dissolved.

Complete step-by-step answer:So in the question it is asked whether the acids get dissociated or ionized. We generally use these two terms taking it as the same but they are different technically.
Before going into the solution first understand the primary difference between these two terms.
Dissociation of a molecule means the process by which charged species are formed which already exists in a compound whereas ionization is a process in which new charged species are formed which did not exist earlier in the compound.
The best example to distinguish between both is NaCl gets dissociated whereas acetic acid reacts with water and gets ionized.
We know that there are two types of acid: strong acid and weak acid.
Strong acids are those species which completely get ionized in aqueous solution, it completely dissociates in water and forms the corresponding charged species.
For example:$HCl\to {{H}^{+}}+C{{l}^{-}}$
But for weak acids, only partial ionization takes place, only about1% of the solution will get ionized into the corresponding ions.
For example:$C{{H}_{3}}COOH\rightleftharpoons C{{H}_{3}}CO{{O}^{-}}+{{H}^{+}}$
As we know that the ionization of the weak acid is an equilibrium then the equilibrium equation and the equilibrium constant can be written as follows:
Take a general case, a weak acid HA dissociates in aqueous solution to produce the ions.
$HA+{{H}_{2}}O\rightleftharpoons {{H}_{3}}{{O}^{+}}+{{A}^{-}}$
The equilibrium constant is written as, ${{K}_{a}}=\frac{[{{H}_{3}}{{O}^{+}}][{{A}^{-}}]}{[HA]}$
Since the water is used as the solvent and the concentration of the solvent is larger, the value is neglected.
Larger the ${{K}_{a}}$ value stronger will be the acid as in the numerator the product concentration is given and hence the${{K}_{a}}$value will be greater for strong acids.

Note:We can also calculate the degree of ionization which gives the ionization yield i.e. the proportion of neutral particles which has changed to charged particles in gaseous or in the aqueous solutions. Greater the value of degree of dissociation then the species is said to dissociate completely in the solution. Smaller the value that species will dissociate partially in the solution.