HCOOH, commonly known as formic acid, is classified as a weak acid. This classification is based on its behavior in aqueous solutions.
When formic acid dissolves in water, it partially dissociates into hydrogen ions (H⁺) and formate ions (HCOO⁻). The dissociation can be represented by the following equation:
HCOOH ⇌ H⁺ + HCOO⁻
Unlike strong acids, which completely dissociate in water, formic acid only partially dissociates. This means that in a solution of formic acid, there will be a mixture of undissociated HCOOH molecules, H⁺ ions, and HCOO⁻ ions. The equilibrium lies far to the left, indicating that only a small fraction of the formic acid molecules dissociate at any given time.
The strength of an acid is often measured by its acid dissociation constant (Ka). For formic acid, the Ka value is relatively low, which further confirms its status as a weak acid. The low Ka value indicates that the acid does not donate protons (H⁺ ions) as readily as strong acids do.
In summary, formic acid is a weak acid because it only partially dissociates in water, resulting in a low concentration of hydrogen ions in the solution.