The most common acid is given the suffix ic . Add the prefix per for the acid with one more oxygen. The suffix ous is given to the acid with one less oxygen. Add the prefix hypo for the acid with two less oxygen atoms. Amphoteric - a substance that acts as either acid or base, depending on what it reacts with.
Water is the most common amphoteric substance.
In the presence of a proton donor, it acts like a base. In the presence of a proton acceptor, it acts like an acid. Anhydrous - without water. Anhydrides are substances that have had water removed. 2 Acid anhydride - an oxide that produces an acid when dissolved in water.