Question

Why is HF a strong acid?

Answer 1

Hint:
You must know what is meant by strong acid and how to classify the strong acid.
You have to know that it fails to completely dissociate in water because it is classified as a weak acid. It again goes by the definition of a strong acid. Usually, if we look at fluorine it has a strong affinity towards hydrogen after dissociation the ions it forms are bound to each other by a strong force
In this we are able to see what is meant by strong acid and why hydrofluoric is considered strong also about their uses.

Complete answer:
Hydrofluoric acid $\left(HF\right)$ is not a strong acid but instead, it is a weak acid. It fails to dissociate completely in water, because of that it is classified as a weak acid. It is against the definition of a strong acid. Usually, if we look at fluorine it has a strong affinity towards hydrogen and it makes a bond with hydrogen.
 A vast amount of energy is required to break the powerful $H-F$ bond in water. There is an extensive hydrogen bonding in $HF$ due to the high electronegativity of fluorine which obstructs the release of hydrogen as $H^{+}$ ions in aqueous solution.
Hydrofluoric acid is a very dangerous chemical and it is quite fascinating. It is not a strong acid from a strict chemical definition. Like $HCl$ or $H_{2}S{O}_4$because of the extreme electronegativity of the fluoride ion a strong acid dissociate completely in water, it is more difficult to get it to separate from the hydrogen ion, so it will only partially dissociate in water, and is therefore considered a weak acid. However, ironically, the strong acid HF is actually more dangerous.
The bond in $HF$ is a polar covalent bond because Fluorine is highly electronegative. So, it becomes easier to remove the proton or hydrogen from the acid. So, then hydrobromic acid $\left(HBr\right)$hydrochloric acid$\left(HCl\right)$ is a stronger acid.

Note:
The solution of hydrogen fluoride in water is known as hydrofluoric acid. Solutions of $HF$ are colourless, acidic and highly corrosive in nature. It is a type of acid which is strongly bonded to hydrogen and the tendency of the molecules to get separated from each other is very less.