The Foundations of Chemistry

H 2 SeO 4 H 2 SO 4 H 2 SeO 3 H 2 SO 3

H 3 PO 4 HNO 3

HBrO 4 HClO 4 HBrO 3 HClO 3

Contrary to what we might expect, H 3 PO 3 is a stronger acid than HNO 2. Care must be

exercised to compare acids that have similar structures.For example, H 3 PO 2 , which has

two H atoms bonded to the P atom, is a stronger acid than H 3 PO 3 , which has one H

atom bonded to the P atom. H 3 PO 3 is a stronger acid than H 3 PO 4 , which has no H atoms

bonded to the P atom.

ACID–BASE REACTIONS IN AQUEOUS SOLUTIONS

In Section 4-9 we introduced classical acid–base reactions. We defined neutralization as

the reaction of an acid with a base to form a salt and (in most cases) water. Most saltsare

ionic compounds that contain a cation other than H
and an anion other than OHor

O^2 . The common strong acidsand common strong basesare listed in the margin. All other

common acids may be assumed to be weak. The other common metal hydroxides (bases)

are insoluble in water.

Arrhenius and Brønsted–Lowry acid–base neutralization reactions all have one thing

in common. They involve the reaction of an acid with a base to form a salt that contains

the cation characteristic of the base and the anion characteristic of the acid. Water is also

usually formed. This is indicated in the formula unit equation. The general form of the

net ionic equation, however, is different for different acid–base reactions. The net ionic

equations depend on the solubility and extent of ionization or dissociation of each reac-

tant and product.

In writing ionic equations, we always write the formulas of the predominant forms of

the compounds in, or in contact with, aqueous solution. Writing ionic equations from

formula unit equations requires a knowledge of the lists of strong acids and strong bases,

as well as of the generalizations on solubilities of inorganic compounds. Please review

carefully all of Sections 4-2 and 4-3. Study Tables 4-8 and 4-9 carefully because they

summarize much information that you are about to use again.

In Section 4-2 we examined some reactions of strong acids with strong bases to form

soluble salts. Let us illustrate one additional example. Perchloric acid, HClO 4 , reacts with

sodium hydroxide to produce sodium perchlorate, NaClO 4 , a soluble ionic salt.

HClO 4 (aq)
NaOH(aq)88nNaClO 4 (aq)
H 2 O(
)

The total ionic equation for this reaction is

[H
(aq)
ClO 4 (aq)]
[Na
(aq)
OH(aq)]88n[Na
(aq)
ClO 4 (aq)]
H 2 O(
)

Eliminating the spectator ions, Na
and ClO 4 , gives the net ionic equation

H
(aq)
OH(aq)88nH 2 O(
)

This is the net ionic equation for the reaction of all strong acids with strong bases to form

soluble salts and water.

Many weak acids react with strong bases to form soluble salts and water. For example,

acetic acid, CH 3 COOH, reacts with sodium hydroxide, NaOH, to produce sodium acetate,

NaCH 3 COO.

10-8

In mostternary inorganic acids, all H
atoms are bonded to O.

384 CHAPTER 10: Reactions in Aqueous Solutions I: Acids, Bases, and Salts

See Saunders Interactive General
Chemistry CD-ROM,Screen 18.2,
Acid–Base Reactions (I).

This is considered to be the same as

H 3 O

OH n 2H 2 O

Common Strong Acids

Binary Ternary

HCl HClO 4

HBr HClO 3

HI HNO 3

H 2 SO 4

Strong Bases

LiOH

NaOH

KOH Ca(OH) 2

RbOH Sr(OH) 2

CsOH Ba(OH) 2