The acetate anion (IUPC name ethanoate ion) is the conjugate base of the dissociation of ethanoic acid. As ethanoic acid is a weak acid it sets up an equilibrium in an aqueous solution. The acetate ions can only be found in small quantities in this equilibrium, which is as follows:
CH3COOH ⇌ CH3COO— + H+
However as this is an equilibrium Le Chatelier's principle can be used. This principle states that the equilibrium will oppose any changes made to the reaction, so at pH's greater than 5.5 there will be a greater yield of acetate ions.
As the acetate ion derives from an acid, it follows that it as a conjugate base will take part in acid base reactions and form salts. A common acetate salt is Sodium acetate (CH3COO-Na+) this salt has many commercial uses some of which include being used as a food additive, or as a ingredient used in portable heating packs.