# Why is HCl a stronger acid than HF?

Jun 26, 2018

$H C l$ is a strong acid, while $H F$ is a weak acid.

#### Explanation:

Acid strength refers to how much an acid ionizes when dissolved in water.

In Arrhenius acid-base theory, an acid is a substance which dissolves in water to release one or more ${H}^{+}$ ions.

A strong acid ionizes completely when dissolved in water. For example, when dissolved in water, every single $H C l$ molecule separates into ${H}^{+}$ and $C {l}^{-}$.

A weak acid only partially ionizes when dissolved in water. For example, when dissolved in water, some $H F$ molecules will separate into ${H}^{+}$ and ${F}^{-}$, but some will remain as $H F$ molecules.

In the case of $H F$, this behaviour can be attributed to the electronegativity of $F$. The $H F$ bond is extremely strong, preventing ionization.

The bond in $H C l$ is comparatively weaker, allowing complete ionization.