Chemistry 1105 Marc McDougal
Unit 7 - Experiment #12: Titration for Acetic Acid in Vinegar 02/272015

Purpose:
The purpose of this lab experiment was to help improve understanding of titration in theory, as well as developing technique to establish the strength of an acetic acid solution. The primary purpose of this experiment was to determine the concentration of an acetic acid solution in the labpaq provided vinegar. As well as define molarity, normality, and weight percent.

Procedure:
For setup, I placed my textbook on top of the labpaq box to hold my clamp with syringe and stop cock attached about 2 centimeters above the 100mL beaker. After getting everything in place I put a white piece of paper underneath the beaker so I could see the color change more clearly. I then filled the syringe up to the 10mL line with the 0.5 M NaOH solution. I opened the stop cock a tiny bit to allow the solution to fill all the way down into the entire rig and ensure there was no air bubbles to allow for an accurate reading. At this time the equipment is all set up for the experiment.
It is now time to perform the experiment. I filled the graduated cylinder with exactly 5mL of the vinegar sample and poured it into the clean beaker. Then I added 2 drops of phenolphthalein solution to the vinegar in the beaker, and placed the beaker containing the vinegar and phenolphthalein under the titrator. After slowly opening the stop cock to allow one drop at a time to drip into beaker, I noticed that the drops were turning a pink color in the beaker. I used one hand to gently swirl the beaker while I kept my other hand on the stop cock to be ready to turn the valve off when the solution stopped dissipating and turned the entire solution pink in color. When the entire solution turned pink throughout, I measured the remaining NaOH in the syringe to determine how much was required to change the solution of vinegar and phenolphthalein. After recording the data, I kept the remaining NaOH in the syringe for further use and thoroughly washed all the other materials. I then repeated the same process two more times.

Observations:

Data Table 1: Quantity of NaOH needed to Neutralize 5 mL of Acetic Acid
Brand of Vinegar Used: Labpaq provided vinegar

Initial NaOH reading
(Interpolate to 0.1 mL)
Final NaOH reading
(Interpolate to 0.1 mL)
Volume of NaOH used
Trial 1
9.5 mL
1.3 mL
8.2 mL
Trial 2
9.6 mL
1.4 mL
8.2mL
Trial 3
9.7 mL
1.4 mL
8.3 mL
Average volume of NaOH used: 8.2 mL

Calculations:
A. Calculate the average number of mL of NaOH used for the 3 trials and record.
The average number of mL of NaOH for this experiment was 8.2 mL.

B. Calculate the Normality of the vinegar using the previously given equation.
.82

C. Calculate the mass of the acetic acid in grams using the previously given equation.
49.2

D. Calculate the percentage of acetic acid using the previously given equation.
4.92

Questions:
A. What is the average % acetic acid in your vinegar sample? Standard vinegar is 5% acetic acid. How does your result compare with the standard?
The average percentage of acetic acid in my vinegar sample was 4.92 percent. With 5% being the standard percentage for standard vinegar, my results were very comparable to that of the standard.

B. Why is it better to use white vinegar rather than dark vinegar for this titration?
White vinegar is the easy choice, being that it contains only acetic acid and water. Dark vinegar contains other chemicals and would make this experiment much more complex.

C. Write a balanced equation for the neutralization of acetic acid