Question

Hydrochloric acid is
a.) Strong acid
b.) Weak acid
c.) Strong base
d.) Weak base

Answer 1

Hint: Hydrochloric acid has a very low value of pka. It gets completely dissociated into ${H^ + }$ cations and $C{l^ - }$ anions when dissolved in any solution. It has a very low value of pka. The higher value of pka indicates greater basicity.

Complete step by step answer:

First, let us understand what an acid or base actually is. Then we will move towards its strength whether strong or weak.

So, an acid can be defined as the chemical species which is capable of donating protons or ${H^ + }$ ions and base is the chemical species which can accept ${H^ + }$ ions. This concept of acid-base was given by Bronsted lowry.

So, if we see hydrochloric acid then it is chemically written as HCl. Here, one H atom combines with one chlorine atom giving the molecule. We know that the octet of chlorine gets complete after sharing one electron with the Hydrogen atom. So, it has no tendency to accept more hydrogen atoms. But HCl has one H atom which it can donate. So, it comes under the category of acids.

Now, we will see which is a strong acid and which one is weak.
This is explained on the basis of dissociation of ${H^ + }$ ions. If the dissociation of the acid is complete i.e. approximately 100% then the acid is said to be strong acid and in case it dissociates to low value then it is a weak acid.
HCl completely dissociates making it a strong acid.


So, the option a.) is the correct answer.

Note:

Acids and bases can be differentiated on the basis of pka value which is inversely proportional to ka value. The ka value is the dissociation constant. If pka value is low, then ka value will be high and acid will be strong.
Hydrochloric acid is stronger than sulphuric acid. The conjugate base formed in this case is $C{l^ - }$ which is a weak conjugate base. So, HCl is a strong acid.