Titration

What is It?

Acid and base combined together Graph of pH as a function of volume of

titrant is called a titration curve

Titration Curve for Strong Acid/Strong Base

Equivalence Point At equivalence point there is the same

moles of acid and base No buffering occurs in strong acid and

base titration What would curve for a strong base

titrated by a strong acid look like?

Example

How many ml of .50 M NaOH are required to reach the equivalence point by titrating 50.0 ml of .40M HBr?

Example: Strong Acid/Base

50.0 mL of 0.200M HNO3 solution is titrated with 0.100M NaOH. What is the pH after the following amounts of base are added?

a) 50.0 mL

b) 100.0 mL

c) 200.0 mL

Weak Acid/Strong Base Titration Curve

pH starts higher Rapid rise and then levels into a zone where

pH doesn’t change much (buffering zone) When enough base added to neutralize ½

acid – called half equivalence pt. (middle of buffer zone and pH = pKa)

pH at equivalence pt is greater than 7

What is the value for the Ka of the weak acid titrated as shown?

Example

Draw a titration curve for a weak base (pH = 11.5 and Kb = 1.8 x 10-5) titrated with a strong acid (pH = 1). On the curve indicate:

a) Equivalence pointb) Buffering zone

c) Where pH = pKb

d) Where pH depends only on basee) Where pH depends only on acid

Polyprotic Acid Curves