The Autoionization of Water
In pure water the following equilibrium is established:
2H2O(l) H3O+(aq) + OH(aq)
This process is called the autoionization of water.
The Ion Product of Water
We can write an equilibrium constant expres
Strong Acids and Bases
The most common strong acids are HCl, HBr, HI, HNO3,
HClO3, HClO4, and H2SO4.
Strong acids are strong electrolytes.
All strong acids ionize completely in solution.
Example: Nitric acid ionizes
Weak acids are only partially ionized in aqueous solution.
There is a mixture of ions and un-ionized acid in solution.
Therefore, weak acids are in equilibrium:
HA(aq) + H2O(l) H3O+(aq) + A(aq)
HA(aq) H+(aq) + A(a
Using Ka to Calculate pH
Using Ka, we can calculate the concentration of H+ (and hence
Write the balanced chemical equation clearly showing the
Write the equilibrium expression. Look up the value for Ka (in
Polyprotic acids have more than one ionizable proton.
The protons are removed in successive steps.
Consider the weak acid, H2SO3 (sulfurous acid):
H2SO3(aq) H+(aq) + HSO3(aq)
Ka1 = 1.7 x 102
HSO3(aq) H+(aq) + SO3
16.8 Relationship Between Ka and Kb
We can quantify the relationship between the strength of
an acid and the strength of its conjugate base.
Consider the following equilibria:
NH4+(aq) NH3(aq) + H+(aq)
NH3(aq) + H2O(l) NH4+(aq) +
Acid-Base Properties of Salt Solutions
Nearly all salts are strong electrolytes.
Therefore, salts in solution exist entirely of ions.
Acid-base properties of salts are a consequence of the reactions of
their ions in solution.
Factors That Affect Acid Strength
For this substance to be an acid:
The HX bond must be polar with H+ and X.
In ionic hydrides, the bond polarity is reversed.
The HX bond is polar with H and X+.
In this case, the
There is a large class of acids that contain a COOH group (a
Acids that contain this group are called carboxylic acids.
Examples are acetic acid, benzoic acid, and formic acid.
Why are these mol
Hydrolysis of Metal Ions
The Lewis concept may be used to explain the acidic
properties of many metal ions.
Metal ions are positively charged and attract water molecules
(via the lone pairs on the oxygen atom of water).