Page 104 - Theory and Problems of BEGINNING CHEMISTRY

CHAP. 6] INORGANIC NOMENCLATURE 93

EXAMPLE 6.13. Write the formulas for (a) lead(II) chlorite and (b) sodium sulfite.
2+
−
Ans. (a) The lead(II) ion is Pb ; chlorite is ClO 2 , having one fewer oxygen atom than chlorate and a single minus
charge. The formula is therefore Pb(ClO 2 ) 2 . It takes two chlorite ions, each with a single negative charge, to balance
+ 2−
one lead(II) ion. (b) The sodium ion is Na . (Sodium forms no other positive ion.) Sulfite is SO 3 , having a 2−
charge. It takes two sodium ions to balance the charge on one sulfite ion, and so the formula is Na 2 SO 3 .
EXAMPLE 6.14. Write the formulas for (a) lithium sulfite, (b) lithium iodite, (c) aluminum sulfate, and (d ) iron(II)
perchlorate.
Ans. (a)Li 2 SO 3 (b) LiIO 2 (c)Al 2 (SO 4 ) 3 (d )Fe(ClO 4 ) 2

6.4. NAMING INORGANIC ACIDS
The anions described in the preceding sections may be formed by reaction of the corresponding acids with
hydroxides:
HCl + NaOH −→ NaCl + H 2 O
H 2 SO 4 + 2 NaOH −→ Na 2 SO 4 + 2H 2 O
H 3 PO 4 + 3 NaOH −→ Na 3 PO 4 + 3H 2 O
+
The salts formed by these reactions consist of cations and anions. The cation in each of these cases is Na ,
− 2− 3−
and the anions are Cl , SO 4 , and PO 4 , respectively. In these examples, the chloride ion, sulfate ion,
and phosphate ion are formed from their parent acids. Thus the acids and anions are related, and so are their
names.
When they are pure, acids are not ionic. When we put them into water solution, seven become fully ionized:
HCl, HClO 3 , HClO 4 , HBr, HI, HNO 3 , and H 2 SO 4 . They are called strong acids. All other acids ionize at least
to some extent and are called weak acids. Strong acids react completely with water to form ions, and weak acids
react to some extent to form ions; but both types react completely with hydroxides to form ions. Formulas for
acids conventionally are written with the hydrogen atoms which can ionize placed first. Different names for
some acids are given when the compound is pure and when it is dissolved in water. For example, HCl is called
hydrogen chloride when it is in the gas phase, but in water it ionizes to give hydrogen ions and chloride ions and
is called hydrochloric acid. The names for all the acids corresponding to the anions in Table 6-5 can be deduced
by the following simple rule. Note that the number of hydrogen atoms in the acid is the same as the number of
negative charges on the anion.
Replace the -ate ending of an anion with -ic acid or replace the -ite ending with -ous acid.

This rule does not change if the anion has a prefix per-or hypo-; if the anion has such a prefix, so does the
acid. If not, the acid does not either.

If the anion ends in -ide, add the prefix hydro- and change the ending to -ic acid.
Ion Ending Acid Name Components

-ate -ic acid
-ite -ous acid
-ide hydro—ic acid

EXAMPLE 6.15. Name the following as acids: (a) HBr, (b) HNO 2 ,(c)H 3 PO 4 ,(d) HClO, and (e) HClO 4 .
Ans. (a) HBr is related to Br , the bromide ion. The -ide ending is changed to -ic acid and the prefix hydro- is added.
−
The name is hydrobromic acid.
(b) HNO 2 is related to NO 2 , the nitrite ion. The -ite ending is changed to -ous acid. The name is nitrous acid.
−
3−
(c)H 3 PO 4 is related to PO 4 , the phosphate ion. The -ate ending is changed to -ic acid, so the name is phosphoric
acid.