Chemical Characteristics of Acids | Acid Properties

2 Categories of Acids:

Monoprotic Acids

Acids can be categorized into two separate groups.  The first group is known as monoprotic acids.  Monoprotic acids donate one proton for each molecule during dissociation (ionization) process.  Some monoprotic acids are nitric acid (HNO3), hydrochloric acid (HCl), and nitric acid (HNO3).  Below is a formula for the ionization of a monoprotic acid.

HA(aq) + H2O(l) H3O+(aq) + A(aq)         Ka

Polyprotic Acids

The other category of acids is known as polyprotic acids.  Polyprotic acids can be also referred to as polybasic acids.  Some examples of polyprotic acids are sulfuric acid (H2SO4), carbonic acid (H2CO3), phosphoric acid (H3PO4), and citric acid (C6H8O7).  These acids are able to donate more than one proton per molecule of acid.  You can break down polyprotic acids into other terms such as triprotic, which donates three protons, or diprotic, which donates two protons.  A diprotic acid, for example, can go through one or two ionizations depending on the pH.  Each ionization has its own constant.  Below are example formulas of this.

H2A(aq) + H2O(l) H3O+(aq) + HA(aq)       Ka1

HA(aq) + H2O(l) H3O+(aq) + A2−(aq)       Ka2


Neutralization is the backbone of titration.  Titration is where a pH indicator shows equivalent points when the identical quantity of moles of a base have been added to an acid.  It is frequently misunderstood that neutralization should result in a pH 7.0 solution.  However, that is only when there are similar acid and base strengths in a reaction.  Neutralization with a weak base and a stronger acid yields acidic salts that are weak.  Ammonium Chloride (NH4Cl) is a great example.  On the other hand, when you neutralize a weak acid with a stronger base, the result is a basic salt that is weak. Sodium Hydroxide (NaOH) is a great example of this.