Explain why acetic acid has four hydrogens, but is a monoprotic acid.
Answered above under another name (John).
Acetic acid, also known as ethanoic acid, indeed contains four hydrogen atoms. However, it is classified as a monoprotic acid because it can only donate one proton (H+) when it ionizes in water.
To understand why acetic acid is monoprotic, we need to look at its chemical structure. Acetic acid consists of a carboxyl group (COOH) and a methyl group (CH3) attached to a central carbon atom.
When acetic acid dissolves in water, it undergoes ionization to form acetate ions (CH3COO-) and hydronium ions (H3O+):
CH3COOH + H2O → CH3COO- + H3O+
The carboxyl group (COOH) is the acidic part of acetic acid because it can donate a proton (H+) to form the hydronium ion (H3O+). However, the methyl group (CH3) does not participate in ionization.
As a result, acetic acid can only donate one proton from its carboxyl group, making it a monoprotic acid.
In summary, while acetic acid contains four hydrogen atoms, it is classified as a monoprotic acid because only one of those hydrogen atoms can be donated as a proton during ionization.