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a sample lab report below is an example of how it should be, all graphs and data will be provided for you, the other file is all the data I have plus the graphs2 attachmentsSlide 1 of 2

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Note: Everything in red are considered pre-lab session and should be turn in a the beginning of the lab session ( if you choose to type up the pre-lab session, please print out 2 copies and paste it to your lab notebook on both the white page and the yellow carbon copy page). Date Name Unknown # (e.g. 1) Group # 1 ( if done in group Partner name ( if done in pairs) Lab #9 Title of the Experiment: ________________________________________________ Purpose: To determine how much acetylsalicylic acid is in commercial aspirin by spectrometry absorbance at 530nm. Introduction: A spectrometer is an instrument that consists of the following parts: a radiation source, a monochrometer, a detector, and a device to read the response of the detector. With a standard curve it is possible to determine the concentration of an unknown using a spectrometer. Reactions: + 3OH-  + H3O+  + [Fe(H2O)6]3  Reagents: Compound Acetylsalicylic Acid Sodium Hydroxide Ferric Chloride MF C9H8O4 NaOH FeCl3 + CH3COO- + 2 H2O + H2O + H2O + H3O+ MW 180.1598 39.99707 162.204 MP 135 318 300 BP 140 1390 315 Study Questions (if any) Type the question and the put the answer immediately after each question Procedure: I. Preparation of a Standard Beer’s Law Curve Observations: Weigh 0.2g acetylsalicylic acid, put in 125mL Erlenmeyer flask 0.2041g White powder Add 5mL 1M NaOH, heat to boiling, 10-15 min Rinse sides of flask with 3-5mL dH2O Cool to RT Quantitatively transfer solution to a 100mL volumetric flask with glass funnel, use dH2O to fill to mark, label this stock solution 18mL Use a 5mL volumetric pipet to transfer 5mL stock to 50mL volumetric flask, fill to mark with 0.02M FeCl3 solution, label A Repeat to make B, C, D, E, by transferring 4, 3, 2, 1 aliquots, respectively (and fill to mark) Measure absorbance at 530nm with FeCl3 as a blank II. Determination of % Aspirin in a commercially prepared tablet Grind up 2-3 Aspirin tablets Weigh 0.2g acetylsalicylic acid, put in 125mL Erlenmeyer flask Kroger (brand) 3 tabs 0.2092g white chunky powder Add 5mL 1M NaOH, heat to boiling, 10-15 min Rinse sides of flask with 3-5mL dH2O Cool to RT Quantitatively transfer solution to a 100mL volumetric flask with glass funnel, use dH2O to fill to mark, label this aspirin solution Use a 2mL volumetric pipet to transfer 2mL stock to 50mL volumetric flask, fill to mark with 0.02M FeCl3 solution, label Unknown 18mL Measure absorbance at 530nm Convert all transmittance to absorbance and determine the concentration of each standard solution Plot a beer’s curve (abs vs. concentration) and determine concentration of acetylsalicylic in aspirin Results: Sample A B C D E F Unknown Transmittance 1.4 3.6 9.2 20.6 44.6 65.0 52.0 Absorbance 1.85 1.44 1.04 0.686 0.351 0.187 0.284 Molarity 0.0011 0.00088 0.00066 0.00044 0.00022 0.00011 0.000185 M = mol / L M = (0.2041 g / 180g/mol) / 0.1L = 0.011M C1V1 = C2V2 C1V1 = C2 V2 C2 = 0.011 ( 0.005, 0.004, 0.003, 0.002, 0.001, 0.0005) = Molarity of A, B, C, D, E, F 0.05L Standard curve 2 y = 1673.3x – 0.0253 1.8 2 R = 0.9979 1.6 Absorbance 1.4 1.2 1 0.8 0.6 0.4 0.2 0 0 0.0002 0.0004 0.0006 0.0008 0.001 0.0012 Concentration Figure 1. Standard curve of known concentrations. M of unknown X = 0.253 + 0.0253 = 0.000185M 1673.3 0.000185M x 0.05L = 0.004625M x 0.1L = 0.0004625mol 0.002L 0.0004625mol x 180g/mol = 0.08325g 0.08325g / 0.2092g Aspirin x 100 = 39.79% Discussion: It was determined by spectroscopy that there is 39.79% Acetylsalicylic Acid in Aspirin. This was determined from a set of standards. A possible source of error in this experiment is that each tablet may contain different amounts of acetylsalicylic acid. Also each tablet did not grind up the coating was difficult to grind and dissolve. Post-lab questions: 1. Then unit of molar absorptivity is cm-1mol-1L. 2. A = bc 0.446 =  1 ( 5.00 x 10-4)  = 892 3. A = bc 0.125 = 892 (1) c c = 1.40 x 10-4
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