Naming acids and bases

Naming Acids

An acid can be described as a substance that yields hydrogen ions (H⁺) when dissolved in water. (H⁺ is equivalent to one proton)

Formulas for acids contain one or more hydrogen atoms as well as an anionic group. The naming of anions end in “-ide” and the prefix ends with “hydro-”. In some cases, two different names seem to be assigned to the same chemical formula and each name depends on its physical state.

HCl hydrogen chloride (gaseous state)

HCl hydrochloric acid (liquid state)

When hydrochloric acid is dissolved in water, the molecules break up into H⁺ and Cl^- ions; in this state, the substance is called hydrochloric acid.

Oxiacids: contain hydrogen, oxygen, and another central element. The formulas of oxoacids are usually written with the H first, followed by the central element and then O. Example of the five common acids as our references in naming oxoacids:

Oxoacids start with reference oxoacid end with “-ic,”

H₂CO₃ carbonic acid

HClO₃ chloric acid

HNO₃ nitric acid

H₃PO₄ phosphoric acid

H₂SO₄ sulfuric acid

We use the following rules to name these compounds:

1. Addition of one O atom to the “-ic” acid: The acid is called “per…-ic” acid. Thus, adding an O atom to HClO₃ changes chloric acid to perchloric acid, HClO₄.

2. Removal of one O atom from the “-ic” acid: The acid is called “-ous” acid. Thus, nitric acid, HNO₃, becomes nitrous acid, HNO₂.

3. Removal of two O atoms from the “-ic” acid: The acid is called “hypo….-ous” acid. Thus, when HBrO₃ is converted to HBrO, the acid is called hypobromous acid.

The rules in naming the anions oxoacids part:

1. When all the H ions are removed from the “-ic” acid, the anion’s name ends with “-ate.” For example, the anion CO₃^2- derived from H₂CO₃ is called carbonate.

2. When all the H ions are removed from the “-ous” acid, the anion’s name ends with “-ite.” Thus, the anion ClO₂^- derived from HClO₂ is called chlorite.

3. The names of anions in which one or more but not all the hydrogen ions have been removed must indicate the number of H ions present.

For example, consider the anions derived from phosphoric acid:

                                                      H₃PO₄        phosphoric acid

     H₂PO^4-       dihydrogen phosphate

 HPO₄^2-       hydrogen phosphate

       PO₄^3-         phosphate

Naming Bases:

A base is described as a substance that yields hydroxide ions (OH^-) when dissolved in water. Some examples are:

NaOH         sodium hydroxide

    KOH           potassium hydroxide

Ba(OH)₂     barium hydroxide

a substance yields hydroxide ions, when dissolved in water, are considered base. Ammonia (NH₃), a molecular compound in the gaseous or pure liquid state, produces hydroxide ions (OH^-) when dissolved into water.  When ammonia dissolves in water, NH₃ reacts partially with water to yield NH⁴⁺ and OH^- ions. Thus, ammonia is classified as a base.