Titration
 Lab technique commonly utilized to determine an
UNKNOWN concentration of a chemical compound with a
KNOWN concentration of another chemical compound.
 Chemical compounds combine with exact stoichiometric
proportions
 Analyte—
 Chemical compound with unknown concentration
 Titrant—
 Chemical compound with known concentration
 Measured with volume and concentration
 Added to chemical compound with unknown concentration in
titration
Acid-Base Titration
 Technique used to perform a neutralization reaction
 Acid/Base with KNOWN concentration used to
determine acid/base with UNKNOWN concentration
 Neutralization Reaction:
 Acid + Base  Salt + H2O
Titration Terminology
 End Point:
 point in a titration where a color change is observed due to
indicator.
 Equivalence Point:
 point during a titration when neutralization has occurred.
 Equal amount of acid and base
 Cannot usually be observed
 We can plot a titration on a graph—titration curve
**Ideally, equivalence point = endpoint **
2 Types of Acid-Base
Titrations
1) Strong Acid/Strong Base Titrations
2) Weak Acid/Strong Base Titrations
1. Strong Acid/Strong Base
Titrations
 Low initial pH value
 Sharp increase in pH before equivalence point
 Equivalence point is pH = 7
 Rapid pH increase after equivalence point
**Indicators with pH range 4-10 helpful for these titrations
**Neutralization reactions
Strong Acid with Strong Base Titrant
Strong Base with
Strong Acid Titrant
Example 1: Strong Acid/Strong
Base Titration Calculations
 30 ml of 0.50M HCl is titrated with 0.50M NaOH.
a) Find the pH of 0.50M HCl
Example 1: Strong Acid/Strong
Base Titration Calculations
 30 ml of 0.50M HCl is titrated with 0.50M NaOH.
b) Find the pH after 15 ml of NaOH added
Example 1: Strong Acid/Strong
Base Titration Calculations
 30 ml of 0.50M HCl is titrated with 0.50M NaOH.
c) Find the pH after 30 ml of NaOH added
Example 1: Strong Acid/Strong
Base Titration Calculations
 30 ml of 0.50M HCl is titrated with 0.50M NaOH.
d) Find the pH after 45 ml of titrant added
2. Weak Acid/Strong Base
Titrations
 High initial pH value
 pH = pKa at half-neutralization
 [weak acid] = [conjugate base]
 Ka = [H3O+] [A -]
[HA]
SO Ka = [A-]/[HA] is 1:1
 Ka = [H3O+], SO
pH = pKa
2. Weak Acid/Strong Base
Titrations
 Equivalence point > 7 on pH scale
**Indicators with pH range > 7 helpful as pH equivalence
point is basic
Example 1: Weak Acid/Strong Base
Titration Calculations
 30 ml of 0.5M HC2H3O2 titrated with 0.50M NaOH.
Ka for acetic acid is 1.8x10 -5.
a) Find the initial pH of 0.5M acetic acid.
HC2H3O2 + OH-

C2H3O2- + H2O (titration view)
HC2H3O2  H+ + C2H3O2- (in detail)
Example 1: Weak Acid/Strong
Base Titration Calculations
 b) Find the pH after 15ml of NaOH were added
 pH = pKa + log [C2H3O2-] / [HC2H3O2]
-used when dealing with buffer solutions
-buffer—mixture of weak acid/conjugate base
-more on this concept later
Example 1: Weak Acid/Strong Base
Titration Calculations
 c) Find the pH at the equivalence point.
 C2H3O2- + H2O  HC2H3O2 + OH-
Example 1: Weak Acid/Strong Base
Titration Calculations
 c) Find the pH after 40ml of NaOH are added to 30ml
of 0.50M HC2H3O2.
Homework
 Titration Worksheet