Question

Why is `HCl` a stronger acid than `HF`?

Answer 1

`HCl` is a strong acid, while `HF` 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 `HCl` molecule separates into `H^+` and `Cl^-`.

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

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

The bond in `HCl` is comparatively weaker, allowing complete ionization.