Naming Acids
Acids are special molecular compounds that contain one or more hydrogen atoms bonded to another
nonmetal. They are a class of covalent compounds with very unique properties. Acids:
 taste bitter (think citrus fruits, lemon heads candy, etc)
 have a low pH
 will change color in the presence of specific indicators
 will always react with a base to form a salt and water
When these compounds are placed in water, the hydrogen atoms separate from the rest of the compound,
and form H+ ions. Although these compounds are made from nonmetal atoms only, they always act as
ionic compounds so those rules (crossover, empirical formulas) need to be applied here.
If the acid has not been mixed with water, it is said to be a “dry acid,” and should be named by ionic
nomenclature.
ex. H2CO4 (s) hydrogen percarbonate
H3P (s) hydrogen phosphide
HNO (s) hydrogen hyponitrite
HI (s) hydrogen iodide
“Wet acids,” those that have been mixed with water, can be formed in three ways:
1. Hydrogen combines with one other nonmetal atom to form a binary acid
ex. HF, HBr, H2S, H3P
2. Hydrogen combines with nonmetal polyatomic ions containing oxygen. These acids are
called oxyacids.
ex. H2SO4, HNO3, H3PO4
3. Hydrogen combines with a carbon, oxygen and hydrogen polyatomic ion to form an organic
acid. These acids are generally written in a different form than the other ternary acids.
Ex. CH3COOH, C6H5COOH, H2C2O4
Naming these compounds depends on the composition of the acid. The word “acid” replaces the need
to name the hydrogen atoms in some acids.
I. To name acids made of hydrogen and any other nonmetal:
1. use the prefix “hydro”
2. use the element’s base name
3. add the ending “ic” and the word acid
ex. HF hydrofluoric acid
HBr hydrobromic acid
HCl hydrochloric acid
H2S hydrosulfuric acid
II. To name acids of hydrogen and polyatomic ions (including organic acids):
1. name the polyatomic ion
if –ate ending use suffix –ic
if – ite ending use suffix –ous
2. add the word “acid”
**If the prefixes “hypo-” or “per-” are present, leave them in the name of the acid.
ex.
H2SO4 sulfuric acid
HNO2 nitrous acid
HClO hypochlorous acid
III. To find the formula for an acid:
1. Recognize that any compound’s name containing the word “acid” means that hydrogen is the first
element listed in the compound’s formula.
2. Look for the prefix “hydro-“. If it is present, that means the compound is made of two elements, H
and one other nonmetal.
To finish writing the formula for these acids:
A. List H first.
B. List the symbol for the element most related to the name of the acid.
Ex. hydrosulfuric acid = sulfur
Hydrochloric acid = chlorine
Hydrophosphoric acid = phosphorus
C. Create a subscript for H based on the charge of the other non metal used in the name.
Ex. hydrosulfuric acid = H2S
Hydrochloric acid = HCl
Hydrophosphoric acid = H3P
3. If the prefix “hydro” is not present,the acid is formed when hydrogen combines with a polyatomic
ion.
“-ic” acid = H + an “-ate” ending polyatomic ion
“-ous” acid = H + an “-ite” ending polyatomic ion
To finish writing the formula for these acids:
A. List H first.
B. List the symbol for the polyatomic ion most related to the name of the acid.
Ex. sulfuric acid = SO4-2
chloric acid = ClO3-1
phosphorous acid = PO3-3
nitrous acid = NO2-1
C. Create a subscript for H based on the charge of the other non metal used in the name.
Ex. sulfuric acid = H2SO4
chloric acid = HClO3
phosphorous acid = H3PO3
nitrous acid = HNO2