363
THE pH OF AQUEOUS SOLUTIONS (SUMMARY)
We are now in a position to summarize the various types of aqueous solutions
we may deal with in chemistry and the computation of the pH of each type.
In these calculations we use the ionization constants of Table 23-1.
1. Pure water (see p 341). The equilibrium reaction is
H 2 0 ?± H
+ + OH[H
+ ] = [OH-] = 1.00 x 10~
7 M
pH = 7
2. Strong acid (see p 342). Because of complete dissociation of acid in dilute
solution,
[H
+ ] = molarity of acid
Thus, for 103 M HC1,
[H
+ ] = 103 M
pH = 3
3. Strong base (see p 343). Because of complete dissociation of base in
dilute solution,
[OH"] = molarity of base
Thus, for 103 M NaOH,
[OH-] = 103 M
pOH = 3
pH = 14 - 3 = 11
4. Weak acid (see p 350). The equilibrium reaction is
HA ?± H
+ + A[H+] = [A-]
[H+][A-] = [H+]
2 = [HA]*,