B convert the t to abs and fill in answers in the

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Physics for Scientists and Engineers with Modern Physics
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Chapter 42 / Exercise 17
Physics for Scientists and Engineers with Modern Physics
Jewett/Serway
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b.Convert the %T to Abs and fill in answers in the table above. c.Prepare a graph Abs vs Concentration. d.From the graph, determine the concentration of the unknown solution.
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Physics for Scientists and Engineers with Modern Physics
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Chapter 42 / Exercise 17
Physics for Scientists and Engineers with Modern Physics
Jewett/Serway
Expert Verified
120 Determining Ascorbic Acid in Vitamin C Tablets PURPOSE: Determine the mass percent of ascorbic acid in a vitamin C tablet by titration with a sodium CHEMICAL EQUATIONS:HC6H7O6(s) + NaOH (aq) NaC6H7O6(aq) + H2O (l) HC6H7O6is the chemical formula for ascorbic acid. MATERIALS:Phenolphthalein (note: flammable and an irritant) NaOH Vitamin C tablet Buret Apparatus BACKGROUND:Ascorbic acid, or vitamin C, is a water-soluble vitamin found in a variety of foods including citrus fruits, tomatoes, and leafy green vegetables. An individual needs for ascorbic acid may vary but the Recommended Daily Allowance (RDA) for adults is 60 milligrams (mg). In this lab we will determine the amount of ascorbic acid in a vitamin C tablet using titration with a NaOH solution. We will compare the results of the titration with the amount of ascorbic acid the manufacture claims to be in the tablet. Example Calculations: Calculate the amount of moles of ascorbic acid in the sample using the known molarity of the standardized NaOH, volume NaOH titrated, and the mole to mole ratio between NaOH and ascorbic acid. ????? ?? ??????𝑖? ??𝑖?= (?????𝑖?? ?? ???𝐻 (?????))(?????? ?? ???𝐻 ?𝑖?????? 𝑖? ?𝑖????) (1 ??? ??????𝑖? ??𝑖?1 ??? ???𝐻)Calculate the mass of ascorbic acid in the sample using the molar mass of ascorbic acid. ???? ?? ??????𝑖? ??𝑖? 𝑖? ?ℎ? ??????, ?= (????? ?? ??????𝑖? ??𝑖?) (????? ???? ?? ??????𝑖? ??𝑖? (????))Calculate the mass percent ascorbic acid in the sample. ???? ???????, % = (???? ?? ??????𝑖? ??𝑖?, ????? ?? ?????? ????, ?) (100%)PROCEDURE:Prepare the Vitamin C Samples 1.Use a mortar and pestle to crush a vitamin C tablet.
121 2.Approximately divide the crushed vitamin C tablet in half, record the mass of each half. 3.Analytically transfer each half of the vitamin C tablet to two flasks labeled Flask 1 and Flask 2. Preparing and Filling the Buret 10.Clean the buret. Fill the buret with water and make sure the stopcock works properly. To clean the buret you can add a small amount of soap solution to a buret brush and scrub the inside of the buret. Rinse several times with tap water and finally with DI water. 11.Set buret on buret stand. Using a funnel add about 5-mL of NaOH, the standard solution, to the buret with the stopcock closed and a waste beaker under the buret. Tilt the buret in order to coat the inside with the standard solution. Pour the standard solution into the waste container. This step will remove any water left behind after the wash. 12.Set the buret back on the buret stand and again using the funnel with the stopcock closed add NaOH, the standard solution, to the buret. Open the stopcock allowing solution to drain out into the waste beaker. Remove any bubbles in the tip of the buret. Record the reading to the 0.01 and the buret is prepared to start the titration. Titrating the Vitamin C Samples 1.Add up to 75 mL of DI H2O into Flask 1. Swirl the flask.

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