PERFORMANCE ASSIGNMENT                  S5c

Determination of the Acid Content in Vinegar

 

Acids and bases react in aqueous solution of form a salt and water.  This reaction is known as a neutralization reaction.  Household vinegar contains acetic acid (HC2H3O2.)

Vinegar can be titrated with a known concentration and volume of base so that the concentration of H+ can be calculated as well as the pH.

 

Procedure:

1. Obtain 25 ml of vinegar and 100 ml of NaOH.  Record the molarity of the NaOH.  Set up a buret in a ring stand.
2. Transfer 25 ml of vinegar to a clean 125 ml Erlenmeyer flask.  Add 3 to 4 drops of phenolphthalein to the flask.
3. Rinse the buret with a little NaOH solution.  Close the stopcock and fill the buret to above the 0.00 line with NaOH.  Open the stopcock and allow a little NaOH to run out into a waste beaker.  Adjust the level of the NaOH so that the bottom of the meniscus is at the 0.00 line.
4. Place the flask containing the vinegar under the tip of the buret.  Add the NaOH by quickly turning the stopcock one half turn.  This allows one drop to leave the buret.  Continue adding NaOH until the solution turns pink.  A white paper under the flask will be helpful.
5. Once the endpoint has been reached record the volume of NaOH that has been added to the flask.
6. Repeat this until two trials are within 0.02 ml of each other.  Calculate the average.

 

Data:

 

	Trial 1	Trial 2	Trial 3
Initial Buret Reading
Final Buret Reading
Volume of NaOH Used
Average Titration Volume
Molarity of NaOH
Volume of Vinegar

 

Analysis

1. Write the balanced chemical equation for the reaction.

 

 

 

2. Calculate the moles of NaOH required to neutralize the HC2H3O2 in the vinegar sample.

 

 

 

 

 

 

 

3. Calculate the molarity of the vinegar sample.

 

 

 

 

 

 

 

 

4. Calculate the grams of HC2H3O2 in the sample.

 

 

 

 

 

 

5. Calculate the % acetic acid in the sample.  The density of the vinegar is 1.0002 g/ml.

 

 

 

 

 

 

6. Calculate the pH of the sample.