The value for this constant is a characteristic of each acid and is something that can be looked up in tables. K a is called the acid dissociation constant . Calculating the pH of a solution of a weak acid or base is a bit more involved than for calculating the pH of a solution of a strong acid or base. The pH of a 0.1 M solution of acetic acid is 2.88. To see how the pH of a solution of a weak acid can be calculated when its pK a and its concentration are known, take a look at the answer given for Question 3 in Study Questions, Set 1 .
Sodium acetate is a weak base and the conjugate base for acetic acid.
The pH of a 0.1 M solution of sodium acetate is 8.88. To see how the pH of a solution of a weak base can be calculated when the pK a of its conjugate acid and its concentration are known, take a look at the answer given for Question 4 in Study Questions, Set 1 . The pK a of a weak acid can be determined experimentally by doing an acid-base titration. A titration of a weak acid is carried out by adding incremental volumes of a strong base to a solution of the weak acid and recording the resulting pH after each addition. The inflection point for this curve occurs at the pH which is numerically equal to the pK a value.