Acetic Acid
Definition and meaning of Acetic Acid in chemistry.
Acetic acid is a weak carboxylic acid with the formula CH3COOH (C2H4O2). It is a colorless liquid with a sharp, vinegar-like odor and is the acid that gives vinegar its taste. Its IUPAC name is ethanoic acid.
In more detail
Acetic acid consists of a methyl group bonded to a carboxyl group (–COOH). As a weak acid with a pKa of about 4.76, it only partially ionizes in water, releasing hydrogen ions and acetate ions. It is the main component of vinegar (typically around 4–8%) and is manufactured on a large scale, mostly by the carbonylation of methanol, for use in making plastics, solvents, and other chemicals.
Key facts
| Formula | CH3COOH (C2H4O2) |
|---|---|
| IUPAC name | Ethanoic acid |
| pKa | About 4.76 (weak acid) |
| Field | Organic Chemistry |
Acetic acid reacts with sodium hydroxide to form sodium acetate and water: CH3COOH + NaOH → CH3COONa + H2O.
Frequently asked questions
Is acetic acid the same as vinegar?
Vinegar is a dilute solution of acetic acid in water, usually around 4–8% acetic acid, so acetic acid is the substance that makes vinegar acidic.
Why is acetic acid a weak acid?
It only partially ionizes in water, at any moment just a small fraction of its molecules have released their hydrogen ion, so it is classed as a weak acid.