CHEMISTRY I - LABORATORY EXERCISE MANUAL

LABORATORY EXERCISE 9: Vinegar Titration

PART I: Memo to Lab Groups

Consumer Information Bureau
CONSUMABLES DIVISION
Washington, D.C.

TO: GenChemCo - Colorado Mountain College
Glenwood Springs, CO

Dear GenChemCo,

Our organization periodically conducts surveys of consumer goods to determine if they are safe, effective, fresh, and comply with all federal regulations.

We would like you to test samples of the three white vinegars we have sent you for their % by mass acid content. Federal mandates specify that commercially retailed white vinegar be no less than 4% by mass acid. In addition, we would like you to determine which of the vinegars is the most economical with regard to its acid content Your findings will be published in our next quarterly Consumer Bulletin. Thank you for your time; we look forward to receiving your report.


Sincerely yours,



R. Ripechecher
Director, CIB






PART II: InterLab Memo


GenChemCo Industries
COLORADO MOUNTAIN COLLEGE


InterLab Memo:

As you can see from the attached letter, our group was asked to determine the % by mass acid content of three white vinegars.

We will titrate 5-ml samples of vinegar with 1M NaOH using the following reaction:

HC2H3O2 (aq) + NaOH (aq) --> NaC2H3O2 + H20

Heinz vinegar $ 2.29/946 ml
Kroger vinegar $ 1.47/473 ml

I would like the class as a whole to brainstorm on the following ideas:

1) How can we use stoichiometry to determine the amount of acid present?

Remember, 1 M NaOH = 1 mol NaOH/1000ml
MW of HC2H3O2= 60 g
g of HC2H3O2/g of sample x 100 = % HC2H3O2 in vinegar tested

2) What techniques can we use to acquire our stoichiometric data?

Each group will need to complete their own analysis of one brand of vinegar and share their data with the other groups so that everybody has complete results. Each group needs to do two complete trials on their brand.

Each group will submit a report two weeks from today which should include the following sections:

I. Initial Working Hypothesis/Objective - Describe the theory on which you will base your procedure

2. Initial Working Plan - Describe the procedure.

3. Data - Be sure to show all measurements and calculations.

4. Analysis of Data - Did the application of the your theory provide valid data and results?

5. Further Steps Taken - Did you have to modify your theory? Did you take any steps above and beyond your initial procedure to reach a conclusion?

6. Letter of Response - Briefly Summarize your methods, findings, and provide the specific information the client asked for.



All contents copyrighted (c) 1998
Peter Jeschofnig, Ph.D., Professor of Science, Colorado Mountain College
All Rights reserved

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This page was created by Peter Jeschofnig and was last updated: 10/30/2001