Page 105 - Theory and Problems of BEGINNING CHEMISTRY

94 INORGANIC NOMENCLATURE [CHAP. 6

(d) HClO is related to ClO , the hypochlorite ion. The prefix hypo- is not changed, but the -ite ending is changed
−
to -ous acid. The name is hypochlorous acid.
−
(e) HClO 4 is related to ClO 4 , the perchlorate ion. The prefix per- is not changed, but the ending is changed to
-ic acid. The name is perchloric acid.

EXAMPLE 6.16. Write formulas for the following acids: (a) nitric acid, (b) chloric acid, (c) hypophosphorous acid, and
(d) perbromic acid.
Ans. (a) Nitric acid is related to the nitrate ion, NO 3 . The acid has one hydrogen ion, corresponding to the one negative
−
charge on the nitrate ion. The formula is HNO 3 .
−
(b) The acid is related to the chlorate ion, ClO 3 . The acid has one hydrogen atom, because the ion has one
negative charge. The formula is HClO 3 .
3−
(c) The acid is related to hypophosphite, PO 2 . The acid has three hydrogen atoms, corresponding to the three
negative charges on the ion. Its formula is H 3 PO 2 .
(d) HBrO 4 .

6.5. ACID SALTS
In Sec. 6.4 the reactions of hydroxides and acids were presented. It is possible for an acid with more than
one ionizable hydrogen atom (with more than one hydrogen written first in the formula) to react with fewer
hydroxide ions, and to form a product with some ionizable hydrogen atoms left:
−
H 2 SO 4 + NaOH −→ NaHSO 4 + H 2 O (Na and HSO 4 )
+
+
−
H 3 PO 4 + NaOH −→ NaH 2 PO 4 + H 2 O (Na and H 2 PO 4 )
+
H 3 PO 4 + 2 NaOH −→ Na 2 HPO 4 + 2H 2 O (Na and HPO 4 2− )
The products formed are called acid salts, and each anion contains at least one ionizable hydrogen atom and at
least one negative charge. The sum of the negative charges plus hydrogen atoms equals the original number of
hydrogen atoms in the parent acid and also the number of negative charges in the normal anion. For example,
−
HSO 4 contains one hydrogen atom plus one negative charge, for a total of two. That is the number of hydrogen
2−
atoms in H 2 SO 4 and also the number of negative charges in SO 4 .
The anions of acid salt are named with the word hydrogen placed before the name of the normal anion.
− 2−
Thus, HSO 4 is the hydrogen sulfate ion. To denote two atoms, the prefix di- is used. HPO 4 is the hydrogen
−
phosphate ion, while H 2 PO 4 is the dihydrogen phosphate ion. In an older naming system, the prefix bi-was
−
used instead of the word hydrogen when one of two hydrogen atoms was replaced. Thus, HCO 3 was called the
bicarbonate ion instead of the more modern name, hydrogen carbonate ion.
EXAMPLE 6.17. Name HSO 4 .
−
Ans. Hydrogen sulfate ion.

EXAMPLE 6.18. What are the formulas for the dihydrogen phosphate ion and ammonium dihydrogen phosphate?
−
Ans. H 2 PO 4 and NH 4 H 2 PO 4 . Note that the two hydrogen atoms plus the one charge total three, equal to the number of
hydrogen atoms in phosphoric acid. The one charge is balanced by the ammonium ion in the complete compound.

6.6. HYDRATES
Some stable ionic compounds are capable of bonding to a certain number of molecules of water per formula
unit. Thus, copper(II) sulfate forms the stable CuSO 4 ·5H 2 O, with five molecules of water per CuSO 4 unit.
This type of compound is called a hydrate. The name of the compound is the name of the anhydrous (without