Question

What is the degree of ionization of a strong acid?

Answer 1

By the very definition of degree of ionization, we know that it can have a maximum value of 1, i.e. completely soluble or dissociated into ions upon adding in water. It can have a minimum value of 0, which implies that it doesn’t get dissolved into water at all. Hence, by knowing about the nature of different types of acid, i.e. weak or strong, we can predict their degree of dissociation.

Complete answer:
In order to understand what could be the degree of ionization of a strong acid, we first need to understand what a strong acid is. A strong acid is defined as the one which gets completely dissociated into hydrogen ions and the respective anion as present in the acid. Hence, it can be represented as:
$HA \to {H^ + } + {A^ - }$
Here, there is complete dissociation.
In case of weak acid, there is dissociation but to a very small extent. This can be represented as shown below:
$HA \rightleftharpoons {H^ + } + {A^ - }$
Here, we can see that the reaction isn’t going to the product side completely. Hence, the dissociation isn’t complete.
Now, the degree of ionization is defined as the ratio of dissociated ions with the number of molecules added in water.
${\text{degree of dissociation = }}\dfrac{{{\text{number of molecules dissociated}}}}{{{\text{total number of molecules added}}}}$
Since in case of strong acid, the dissociation is complete, hence the number of molecules dissociated are equal to the number of molecules added in water.
Hence, the degree of dissociation of strong acid is equal to $1$ .

Note:
The value of the degree of dissociation of all strong acids can be taken as $1$ . However, the same cannot be quantified for all the weak acid or weak bases. Since when weak, they will have their own value of degree of dissociation based on the quantification of their weakness. Hence, all strong acid’s degree of dissociation can be said as $1$ in general, but the same cannot be done for all weak acids/bases.