CHEM 211 Laboratory



CHEM 212 Laboratory

Redox Titration of Oxalate in K3[Fe(C2O4)3].3H2O

Reference: General Chemistry Laboratory Experiments, Suzanne W Slayden, 1999, 3rd edition, Pages 121-126

Purpose: The purpose of this experiment is to determine the experimental weight percent of oxalate in the K3[Fe(C2O4)3].3H2O sample.

Procedure and Observations: Follow the instructions given in the lab manual. Record all your data in your laboratory notebook as you proceed with the experiment.

Data: After you have noted down all the masses, volumes and molarities, enter your own data into the appropriate Web-based data entry form, using a computer in the lab. In your measurements and calculations, remember to pay attention to uncertainties and significant figures.

Results: Outside of class, retrieve your data in spreadsheet form (along with that of the entire class) from: . Then use Excel to calculate the Mass of samples, Volume of KMnO4, Moles of KMnO4, Moles of C2O4 2- and Weight of oxidized C2O4 2-, Experimental weight percent of oxalate, Average percent weight oxalate, Standard deviation, Theoretical weight percent oxalate, and Percent Error.

Your lab report should include the following in addition to the pages from your lab notebook:

• An Excel sheet “Raw Data” showing the raw data for the entire class (as downloaded).

• A 2nd Excel sheet “Class Results” showing the calculated results for each student in the class – each in a separate row. Make sure to show an example calculation for each column. This can be done by copying the equation to a blank cell below the elements in the table. An apostrophe in front of it makes it text instead of an equation. Each table should be formatted as in previous classes with lines separating the table headings from the contents. A line below the contents should also be drawn. The columns should include:

o Mass of samples

o Volume of KMnO4

o Moles of KMnO4

o Moles of C2O4 2-

o Weight of oxidized C2O4 2-

o Experimental weight percent of oxalate for each titration

o Average weight percent oxalate

o Standard deviation

o Theoretical weight percent oxalate

o Percent Error

• An Excel chart showing a histogram of the distribution of experimental weight percent results. Use equally spaced “bins” chosen to display the “spread” in the class results.

Discussion: In your discussion section address the following questions:

• Why is an indicator not required in Permanganate titrations?

• Why is the Potassium permanganate solution standardized before you analyze your compound?

• What are the possible sources of error in this experiment? Refer in your answer to the class histogram as well as to your own results.

Printing Tables:

• Large tables should be printed in the landscape mode and sometimes it might be necessary to go to “page setup” and select “Fit to 1 page” to make the page fit on one page.

• Include column and row headings on the printout so that the instructor can more easily understand equations used. This can be done by going to File → Page Setup → Sheet tab → Select “Row and Column Headings”.

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