4. In the experiment TLC: (a) When the best separations are achieved, what values range do R, fall between? (3 points) (b) A student analyzed a sample by TLC and developed it with a mixture solvent, 20% methanol in CH2Cl2. The developed TLC plate is shown below. Please improve the separation condition and explain. You don't need to calculate. (5 points) OCH На OCH

4. In the experiment TLC: (a) When the best separations are achieved, what values range do R, fall between? (3 points) (b) A student analyzed a sample by TLC and developed it with a mixture solvent, 20% methanol in CH2Cl2. The developed TLC plate is shown below. Please improve the separation condition and explain. You don't need to calculate. (5 points) OCH На OCH

Chemistry

10th Edition

ISBN:9781305957404

Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Chapter1: Chemical Foundations

Section: Chapter Questions

Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...

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The following data are for a GLC column: L= 35.5 cm, flow rate = 0.303 mL/min A chromatogram of a mixture of the following compounds provide the following data: (min) (min) Air 0.9 | Benzene 5.0 0.71 Toluene 7.9 0.82 Xylene 8.4 1.16 Calculate: a. The number of plates from each peak. b. The mean for N. C. The plate height H. From the data above, calculate the resolution for d. Benzene and toluene. e. Toluene and xylene. F. Benzene and xylene. g. The length of column required to achieve an average resolution of 4.50.
4 You were assigned to determine the concentration of an unknown starch solution. [This unknown is different from Dr. Ford's unknown.] So you prepared a cuvette by mixing 5 drops of your unknown starch solution + 5 drops of water +3 mL buffer + 1 drop of iodine. You used the same spectrophotometer Dr. Ford used to measure the absorbance of your unknown starch mixture and the absorbance was 0.127. What is the concentration (in micro-g starch/micro-L) of your unknown starch solution? Assume that 1 drop of the unknown out of starch solution = 40 micro-L. Give a numerical answer with 3 sig figs without any unit. Answer:
tras 12. A standard stock solution is diluted to generate three working standard solutions containing ethyl acetate (EA) at 50 ppm, 400 ppm, and 800 ppm. An internal standard, n-butanol (nB), is added so its concentration is 1500 ppm in each of the working standard solutions. The solutions are analyzed using GC- FID. The peak area data for the peak corresponding to ethyl acetate from the standard chromatograms 50 ppm (EA area = 5.05, nB area = 124.37) 400 ppm (EA area = 47.98, nB area = 125.31) 800 ppm (EA area = 98.21, nB area = 98.21, nB area = 130.63) The results for the linear regression analysis for the data set using Excel are: m = 0.7065, b = 0.002134 m = 1.4251, b = -0.003901 m = 1.4215, b = -0.003091 m = 0.7015, b = 0.002231
A mixture of three components is separated using paper chromatography, and each component is analyzed using absorption. With standards containing 100 ppm of each component run simultaneously, the following data were obtained: cmpd A, 0.72 absorbance; B, 0.55; C, 0.80. For the unknown mixture, the data obtined when run under identical conditions were as follows: cmpd A, .0.15 absorbance, B, 0.84; C, 0.75. a) Calculate the relative percentage composition of the unknown mixture. b) The distances traveled by the three components were 8.5, 6.3, and 5.5 cm, respectively. Sketch the appearance of the paper chromatogram. Label each spot. c) Calculate the Rf values if the solvent front is 18 cm.
10:06 ( nour Screen Shot 2021-09-21 at 10.0.. Sort the following molecules in order of increasing Rf value assuming a normal-phase silica TLC plate was used with a 10:1 hexanes: ethyl acetate solvent system. NH2 HN 1 2 3 4
The figure below shows a portion of a GC chromatogram for a mixture of two aromatic compounds labeled A and B. The separation employed a 2.50 meter packed column under isothermal conditions (90 °C) and a flow rate of 10 mL/min. in (c) Detector Signal 300.0 250.0 200.0 150.0 100.0 50.0 0.0 1.0 Unretained 1.2 1.3 1.4 1.5 time (min) Calculate the retention factors for each peak. 1.5
state the three different modes of GC/MS, and explain more for each.
A 19.8474 gram vial is used to calculate ethe partition coefficient of benzoic acid in a 50/50 DCM/water mixture using 59.9 mg of benzoic acid. If the vial + benzoic acid from the DCM layer weighs 19.8819 grams, what is the partition coefficient (DCM/water)?
5. A mixture was analyzed using TLC and it was doubted to contain three components: R, T, and Y. A non polar solvent was used with a polar stationary phase. Answer the following questions: cm 9. solvent front origin line R T Yrple Y mpte before lofter Which of the doubted components (R, T or Y) are present in the sample? Are there other components in the sample? What are the Rr values ofR and T?
An analyte with a partition co-efficient of 4.0 is extracted from 10 mL of the aqueous phase (Phase 1) into an organic Phase (Phase 2). What volume of the organic phase is needed to extract 90% of the analyte in four extraction using equal volumes? (Show your Calculation)