Laboratory assignment for module 4: equilibrium constants

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Thomas Edison State College

General Chemistry II with Labs (CHE-122)

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LABORATORY REPORT

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 = 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:

 

 

 

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)