Acetic acid, formula CH3CO2H, is the second smallest carboxylic acid and is larger than only formic acid, HCO2H. Vinegar's tart taste and distinctive odor is due to the presence of acetic acid. It is a common reagent in organic synthesis.
 Physical properties
Molecular weight: 60.05 mg/mol. Vapor pressure at 20°C: 12 Torr. Melting point: 16°C. Boiling point: 118°C.
Acetic acid has a pKa value of 4.76, which makes it a fairly weak acid, as most organic acids are. In dilute solutions, acetic acid dissociates into the acetate ion and the hydronium ion. The degree is dissociation is determined by the pH of the solution.
Acetic acid is generally purchased as Glacial acetic acid
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