Percent Dissociation of Weak Acids
Objective :
Determine percent dissociation of acetic acid in various concentrations and study
the relationship between concentration and percent dissociation.
Prelab Questions :
(PL1) What is the pH of 1.00M acetic acid (Ka = 1.8x10^-5)
(PL2) What is the percent dissociation for PL1?
(PL3) What is the pH of 6.00M acetic acid (Ka = 1.8x10^-5)?
(PL4) What is the percent dissociation for PL3?
(PL5) Comparing answers to PL2 and PL4, what is the relationship between
concentration and percent dissociation?
(PL6) 0.050 M HF (Ka = 3.5x10^-4) solution has pH of 2.40. What is the percent
dissociation for this solution?
Procedure :
(1) Take pH of 5 acetic acid solutions of various concentrations, 0.10M, 0.50M,
1.00M, 3.00M, 6.00M.
Calculations :
(C1) Calculate percent dissociation of 5 solutions. Make sure to have ICE table
for each clearly labeled.
(C2) Draw a graph of percent dissociation vs. concentration.
Post Lab Questions :
(Q1) What was the calculated pH of 1.00M acetic acid (from PL1)? The
experimental pH of 1.00M acetic acid (from your data)? Explain.
(Q2) What was the calculated pH of 6.00M acetic acid (from PL3)? The
experimental pH of 6.00M acetic acid (from your data)? Explain.
(Q3) What was the relationship between the concentration and percent
dissociation according to calculations (from PL5)? What was the experimental
relationship between the concentration and percent dissociation (from your
data)? Explain.
Summary :
Graph properly labeled.
0.10M
pH
% dissociation
0.50M
1.00M
3.00M
6.00M