Laboratory Assignment for Module 4: Equilibrium Constants
(eScience Lab 5 [17])

Table 1. Equilibrium Constants Data

III. CALCULATIONS (15 POINTS)

Volume of NaOH when solution turns dark pink/orange:

Volume of NaOH at the equivalence point (the point on the graph midway between the vertical rise; see Lab 7 [19], Figure 2):

pH at the equivalence point (should be approximately 8–9):

Volume of NaOH at equivalence point:

Volume at half-equivalence point:

pH at the half-equivalence point:

pH = pK_a  at this point

K_a (equilibrium constant):

pK_a = –log K_a                                    

Show calculations

IV.  RESULTS (20 POINTS)

Experimental K_a of acetic acid:

Theoretical K_a of acetic acid:

1.      Compare your experimental value for the equilibrium constant to the theoretical value. Do you notice any variation? If so, why? (10 points)

2.      Write the dissociation of acetic acid, HC₂H₃O₂.(10 points)

3.      Write the equilibrium expression for acetic acid. (10 points)