-Acids and Bases are classes of compounds that may be identified by observable properties.  Acids taste tart or sour, reacts with metals to produce hydrogen gas, and turn a blue litmus paper to red. Bases taste bitter, feel slippery, and turn red litmus paper to blue. Both acids and bases are electrolytes. An acids and bases will neutralize each other properties.

Acids and Bases may be described according to Three Major Theories:

• The Arrhenius Theory

Defines an acid as a substance that produces hydrogen ions in solution and a base produces hydroxide ions in solution.

      Arrhenius Acid in water solution produces H+ as the only positive ion.

 

 

 

 

 

 

 

 

 

 

 

Notice: All Formulas of acids each begin with H. This emphasizes that the  acids are sources of H+ ions .

 

      Arrhenius Base in water has a bitter taste, feels slippery to touch, gives characteristic colors to indicators, and neutralize acid.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

​The Bronsted-Lowry Theory

Defines an acid as proton (or hydrogen ion ) donor and a base as a proton acceptor.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The Lewis Theory

This concept is more general either the Arrhenius theory or the Bronsted-Lowry theory.  A Lewis acid is an electron-pair acceptor. A Lewis base is an electron-pair donor. A hydrogen ion (Bronsted-Lowry acid) can accept  pair of electrons in forming a bond. A hydrogen ion, therefore, is also a Lewis acid. A substance that accepts a hydrogen ion (Bronsted-Lowry base) must have a pair of electrons available ( Lewis base). Consider the reaction of H+ and OH-

 

                                 

                                         

 

 

 

                                                        Lewis Acid   Lewis base

                A hydrogen ion is a Lewis base. It is also a Bronsted-Lowry base.

                A hydrogen ion is both a Lewis acid and a Bronsted-Lowry acid.

The Lewis theory also includes some compound that are not classified as Bronsted-Lowry acids and bases.

 

Source:

PhoenixScienceSeries-Chemistry

 

 

 

 

Written by: Nina Manuel