AssignmentOne - Explain how you can use standard volumetric...

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Take Home Assignment #1 Please turn in neatly worked solutions for the following problems. Answers are due by 4:00 PM on Friday, August 31 st . 1. Erythrosin B (which we will abbreviate as EB) is a dye with many analytical uses, including a biological stain for bacteria in soil, a plasma stain for nerve cells (when used in conjunction with the dye methylene blue), a phosphorescent probe for studying the diffusion of membrane proteins, and as an acid-base indicator. The chemical formula for the sodium salt of EB is C 20 H 6 O 5 I 5 Na 2 . Suppose you take a 0.2519-g sample of a 0.116% w/w EB mixture, transfer it to a 25-mL volumetric flask, and dilute to volume. What is the concentration of EB in the resulting solution? Report your answer using units of molarity, % w/v, and ppm being careful to report each with an appropriate number of significant figures. 2. Suppose you have a stock solution that is 20.00 ppm in EB.
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Unformatted text preview: Explain how you can use standard volumetric glassware to make a solution that is 1.280 ppm EB. Table 4.2 on page 59 of your text lists the types of transfer pipets and volumetric flasks available to you. You many use any combination of these that you desire and may use more than one dilution. There are many solutions to this problem. 3. To determine the amount of iron in a dietary supplement (in which iron is present as FeSO 4 •7H 2 O), a random sample of 15 tablets weighing a total of 20.505 g was ground into a fine powder. A 3.116-g sample of the powdered tablets was dissolved and treated with NaOH, precipitating the iron as Fe(OH) 3 . The precipitate was collected, rinsed, and ignited to a constant weight as Fe 2 O 3 , yielding 355 mg. Report the average iron content of the dietary supplement as g FeSO 4 •7H 2 O per tablet....
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This note was uploaded on 04/02/2012 for the course CHEMISTRY 222 taught by Professor Mcdonald during the Fall '11 term at University of Illinois, Urbana Champaign.

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