Consumer Chemistry: Determining the Iron Content in Supplements

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Stockton University *

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2150

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Chemistry

Date

Dec 6, 2023

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pdf

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2

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CHEM 2115 Lab Report Experiment #8 Iron Content of Vitamins Chem I Lab N ame Samuel Zheng Section # 009 Station # D4 Date 11/26/2023 A. Preparation of Standard Curve Attach a copy of your previously prepared standard curve with the equation of the best-fit line included on the plot. B. Vitamin Unknowns – Data & Calculations Tablet Name ShopRite Iron Mass (on label) of iron per tablet (mg) 65 Be sure to include the necessary units for the values reported in the above tables. Attach sample calculations of each type necessary to obtain the results in the above table. These should include the equations used, substituted values, appropriate units, and results. C. Class Data Analysis Class data for this experiment can be downloaded from a Blackboard file in which each student will have entered the brand of tablet studied, the mass of iron from the label, and the absorbance of Solution 3. For each brand, compute the average mass of iron per tablet as determined experimentally. Then compute the relative error compared to the mass of iron per tablet indicated on the label. Complete the following detailing the results of your data analysis. The table has four columns: Tablet name, Mass iron per tablet, label (mg), Mass iron per tablet, experimental (mg), and Relative Error (%). Note any data points that were discarded in the averaging and justify their exclusion from your calculations Trial 1 Trial 2 Measured Absorbance (Solution 3) 0.908 1.057 Concentration of iron (Fe +2 ) in Solution 3 2.26 2.63 Concentration of iron (Fe +2 ) in Solution 1 910.2 1060 Mass of iron in tablet 91.02mg 106mg Average mass of iron in tablet 98.51 mg Relative Error (compared to mass on label) 51.55%
Excluded data points & justification: D. Questions 1. Comment on the relative error in your data and the class data. What are possible sources of error that could lead to the observed differences between the mass of iron per tablet listed on the label and the mass per tablet determined experimentally? Be specific, for example “human error” is not an acceptable. Your sources of error should be consistent with the observed differences. The relative error for Tablet A, B, and C respectively are 2.18%, 8%, and then 13.29%. Some sources of error may include adding too much water to the flasks, tablets not fully dissolved in the acid, and then not calibrating the spectrophotometer correctly. 2. Suppose that a student does not remove fingerprints from the cuvette before the absorbance of a test solution is measured. What would happen to the measured absorbance? Would the calculated mass of iron in the tablet for this trial be too large, too small, or unaffected by this error? Explain why. If fingerprints were not removed using the Kimwipe, then the light will not be able to pass through the cuvette effectively. The measured absorbance will be affected because of this. The mass of the iron will be too high since not enough light was passed through. 3. Suppose a student analyzes an unknown tablet as described in the experimental procedure and the absorbance of the resulting Solution 3 is determined to be 1.250, which is higher than any value from your standard curve. What might the student do in order to determine the amount of iron in this sample without making new standard solutions? A student can add more water to dilute the tablet to determine the amount of iron in the sample without the need to make new standard solutions. A smaller volume can be taken into account as well. Tablet N ame Mass iron per tablet, label (mg) Mass iron per tablet, experimental (mg) Relative error (%) A 45 44.15 2.18% B 28 30.24 8% C 65 56.36 13.29%
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