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

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)