7.3. Acids and Bases http://www.ck12.org
FIGURE 7.7
(A) Vinegar comes in a variety of types,
but they all contain acetic acid. (B) Cit-
rus fruits like grapefruit contain citric and
ascorbic acids.exhibited by ionic compounds like NaCl. However, when these molecules are dissolved in water, the chemical bond
between the hydrogen atom and the rest of the molecule breaks, leaving a positively-charged hydrogen ion and an
anion. For example, the following chemical equation describes what happens when the acid HCl is dissolved in
water:
HCl→H++Cl−Since acids produce H+cations upon dissolving in water, the H of an acid is written first in the formula of an
inorganic acid. The remainder of the acid (everything except the H) constitutes the anion that is formed after the
acid dissolves. Organic acids are also an important class of compounds, but the rules for naming them are different,
and they will primarily be discussed in a later chapter. Abinary acidis an acid that consists of hydrogen and one
other element. The most common binary acids contain a halogen. Anoxoacidis an acid that consists of hydrogen,
oxygen, and a third element. The third element is usually a nonmetal.
Naming Acids
Since all acids contain hydrogen, the name of an acid is based on the anion that goes with it. Recall from earlier in
the chapter that anions can either be monatomic or polyatomic. The names of all monatomic ions end in–ide. The
majority of polyatomic ions end in either–ateor–ite, though there are a few exceptions, such as the cyanide ion
(CN−). It is the suffix of the anion that determines how the acid is named, as described in the rules and the table
below (Table7.9).
The three different suffixes that are possible for the anions lead to the three rules below.
- When the anion ends in–ide, the acid name begins with the prefixhydro-. The root of the anion name goes in
the blank (e.g.,chlor-for chloride), followed by the suffix–ic acid. HCl is named hydrochloric acid, because
Cl−is a chloride ion. HCN is hydrocyanic acid because CN−is a cyanide ion. - When the anion ends in–ate, the name of the acid is the root of the anion followed by the suffix–ic acid.
There is no prefix. H 2 SO 4 is sulfuric acid (not sulfic) because SO 42 −is the sulfate ion. - When the anion ends in–ite, the name of the acid is the root of the anion followed by the suffix–ous acid.
Again, there is no prefix. HNO 2 is nitrous acid because NO 2 −is the nitrite ion.
Note that the root for a sulfur-containing oxoacid issulfur-instead of justsulf-. The same is true for a phosphorus-
containing oxoacid, which usesphosphor-as its root instead of simplyphosph-.