Experiment: What is the Relationship Between Acid
Concentration and % Dissociation
Chemistry 160
Objective
Determine percent dissociation of acetic acid in various concentrations and study the
relationship between concentration and percent dissociation.
Introduction
Weak acids can dissociate in an aqueous solution to achieve equilibrium. The percent
dissociation is defined as follows:
Percent dissociation = amount dissociated (mol/L) / initial concentration (mol/L) x 100%
For example,
HC2H3O2 (aq)  H+ (aq) + C2H3O2- (aq)
The equilibrium expression is:
Ka = 1.8 x 10-5 = [H+][C2H3O2-] / [HC2H3O2]
The percent dissociation can be calculated as:
Percent dissociation = [H+] (final) / [HC2H3O2] (initial)
Procedure
Measure pH of 5 acetic acid solutions of various concentrations, 0.10M, 0.50M, 1.00M, 3.00M,
6.00M.
Calculations
1. Determine the % dissociation for each solution. Be sure to create ICE tables for each solution.
Do all calculations during class and in your notebook.
2. Use EXCEL to create a data table, graph (% dissociation vs. concentration), and one other
method of illustrating your data. Be sure to print and tape into your notebook!!
Pre-Lab Questions
1. Do problem 18.77 in your textbook (one of your HW problems!).
Post Lab Assignment
1. Submit data table and all EXCEL work
2. Submit one sample calculation (including an ICE table)
3. Write a 1 page (double space) discussion of your results
4. Write an Abstract