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Nomenclature of Inorganic Acids and Bases

This is part of the HSC Chemistry course under the topic Properties of Acids and Bases.

HSC Chemistry Syllabus

  • investigate the correct IUPAC nomenclature and properties of common inorganic acids and bases (ACSCH067)

How to name inorganic acids and bases

This video discusses the nomenclature (naming convention) of various inorganic acids and bases.

Nomenclature – Naming Acids

Acid names apply to the following two different groups of acids:

  • binary acids do not contain oxygen (particularly hydrohalic acids).
  • oxoacids (oxyacids) are inorganic compounds made up of oxygen.

 

Hydrohalic acids

  • Hydrohalic acids are aqueous solutions of binary inorganic compounds in which hydrogen, H, is combined with a halogen (Group 17) element.

 

Molecular formular

Prefix

+

Modified name of element

+ acid =

“acid” name

HF

Hydro

+

Fluorine + ic

+ acid =

Hydrofluoric acid

HCl

Hydro

+

Chlorine + ic

+ acid =

Hydrochloric acid

HBr

Hydro

+

Bromine + ic

+ acid =

Hydrobromic acid

HI

Hydro

+

Iodine + ic

+ acid =

Hydroiodic acid

 

Oxyacids

  • Oxoacids (or oxyacids) are inorganic compounds made up of oxygen (O), hydrogen (H) and one other element (E) called the central atom or central element.
  • Examples of molecular formula and their corresponding possible structures showing the general relative positions of hydrogen (H), oxygen (O) and the central element (E) are shown below:
  • Oxoacids are named with the name of the central element first using a modified ending (suffix) to indicate the relative amount of oxygen present, followed by the word "acid"
Structure of inorganic oxyacids

 

Non-halogenic oxyacids

  • The "ic" suffix indicates more oxygen is present in the compound than for the "ous" suffix. The table below includes compounds containing oxygen and hydrogen and one other element that is not a halogen (Group 17) element.

 

Table: naming nomenclature of oxyacids where the central atom is not a halogen.

Central element in oxyacid

Most oxygen

(highest oxidation state)

Least oxygen

(lowest oxidation state)

Nitrogen

Nitric acid (HNO3)

Nitrous acid (HNO2)

Phosphorus

Phosphoric acid (H3PO4)

Phosphorous acid H3PO3

Sulfur

Sulfuric acid (H2SO4)

Sulfurous acid (H2SO3)

 

Nitric acid is a monoprotic oxyacid. One molecule of nitric acid can only donate one proton.

structure of nitric acid

 

Sulfuric acid is a diprotic oxyacid. One molecule of sulfuric acid can donate up to two protons. 

Structure of sulfuric acid

 

Phosphoric acid is a triprotic oxyacid. One molecule of phosphoric acid can donate up to three proton.

Structure of phosphoric acid

 

Halogenic oxyacids

Halogenic oxyacids

  • perhalic acid has the most oxygen of all with the general molecular formula HXO4
  • halic acid has less oxygen than perhalic acid and has the general molecular formula HXO3
  • halous acid has less oxygen than halic acid has the general molecular formula HXO2.
  • hypohalous acid has the least oxygen of all and has the general molecular formula HXO

 

Table: naming nomenclature of oxyacids where the central atom is a halogen.

Central element in oxyacid

More oxygen

(highest oxidation state)

Less oxygen

(lowest oxidation state)

Chlorine

Perchloric acid (HClO4)

Chloric acid (HClO3)

Chlorous acid (HClO2)

Hypochlorous acid (HClO)

Bromine

Perbromic acid (HBrO4)

Bromic acid (HBrO3)

Bromous acid (HBrO2)

Hypobromous acid (HBrO)

For example, the structures of halogenated oxyacid containing chlorine as the central atom are shown:

Structures of chlorine oxyacids

Nomenclature for Inorganic Bases

The naming convention of inorganic bases follows nomenclature of ionic compounds.

Metal hydroxides:

  • NaOH – sodium hydroxide

Non-metal hydroxides:

  • `NH_4OH` – ammonium hydroxide

Metal (hydrogen) carbonates:

  • `NaHCO_3` – sodium hydrogen carbonate
  • `Na_2CO_3` – sodium carbonate

Common Acids and Bases

Table: common examples of strong and weak acids

Strong acids

Weak acids

Molecular formula

Name

Molecular formula

Name

HClO4

Perchloric acid

H3PO4

Phosphoric acid

HI

Iodic acid

HF

Hydrofluoric acid

HBr

Hydrobromic acid

CH3COOH

Ethanoic acid (acetic acid)

H2SO4

Sulfuric acid

CH2OOH

Methanoic aicd

HCl

Hydrochloric acid

C6H8O7

Citric acid

HNO3

Nitric acid

C2H2O4

 Oxalic acid

 

Table: common examples of strong and weak bases. Note that most weak bases are organic bases (containing carbon). 

Strong bases

Weak bases

Molecular formula

Name

Molecular formula

Name

NaOH

Sodium hydroxide

NH3

Ammonia

KOH

Potassium hydroxide

NaHCO3

Sodium bicarbonate

Ba(OH)2

Barium hydroxide

CH3NH2

Methylamine

Ca(OH)2

Calcium hydroxide

(CH3CH2)2NH

Diethylamine

 

  

BACK TO MODULE 6: ACID/BASE REACTIONS