Acids, Bases, Arrhenius

Learning Goals

You will learn the definitions of acid and base according to the model of Arrhenius.

Synopsis

The word acid comes from a word that means sour. The word alkali comes from a word that describes the remains left after burning certain plants and these remains feel rather slippery when wet. The word salt probably originates from a word meaning sea salt. Later a salt was defined as a product of the reaction of an acid with a base. The definition of acid according to the Swedish chemist Arrhenius is any compound that can release a hydrogen atom upon ionic dissociation of the compound in water solution. Arrhenius defined a base as a substance that can produce a hydroxide ion in a water solution. NaOH is obviously an Arrhenius base for it dissociates in water to Na+ and OH-. However, ammonia is also a base, for in water it forms the hydroxide ion. The source of the hydroxide ion does not have to be the "base." The reaction of an acid and a base will produce a salt. The Arrhenius definition limits the concept of acid and base to water solutions. We will study other models that are not so limited.

Review Question

  1. Show by a balanced chemical equation how each of the following is classified as a base by the Arrhenius model: Ba(OH)2, NH3, and H2O.
  2. Show by a balanced chemical equation how each of the following is classified as an acid by the Arrhenius model: HCl, CH3COH, and H2O.


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Web Author: Dr. Leon L. Combs
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