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

Question: #491

I.       PURPOSE (10 POINTS)

II.    TEST DATA (15 POINTS)

Table 1. Equilibrium Constants Data

Syringe Reading, mL


pH after each 0.5 mL increment


Color Observations

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 = pKa at this point

Ka (equilibrium constant):

pKa = –log Ka

Show calculations

IV.RESULTS (20 POINTS)

Experimental Ka of acetic acid:

Theoretical Ka of acetic acid:

IV.CONCLUSION (10 POINTS)

V.QUESTIONS (30 POINTS)

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)

Solution: #510

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

Volume of NaOH when solution turns dark pink/orange: 4.5 mL

Volume of NaOH at the equivalence point (the point on the graph midway between the vertical rise; see Lab 7 [19], Figure 2): 4.6 mL...