DATA FROM RECRYSTALLIZATION EXPERIMENT Weight of crude benzoic acid, g 0.2498 Weight of filter paper, g 1.0211 Weight of filter paper with crystal, g 1.215 Weight of recrystallized benzoic acid, g % Recovery DATA FROM SUBLIMATION EXPERIMENT Weight of crude benzoic acid, g 0.1104 Weight of filter paper, g 0.9887 Weight of filter paper with crystal, g 1.0318 Weight of recrystallized benzoic acid, g % Recovery

DATA FROM RECRYSTALLIZATION EXPERIMENT Weight of crude benzoic acid, g 0.2498 Weight of filter paper, g 1.0211 Weight of filter paper with crystal, g 1.215 Weight of recrystallized benzoic acid, g % Recovery DATA FROM SUBLIMATION EXPERIMENT Weight of crude benzoic acid, g 0.1104 Weight of filter paper, g 0.9887 Weight of filter paper with crystal, g 1.0318 Weight of recrystallized benzoic acid, g % Recovery

Appl Of Ms Excel In Analytical Chemistry

2nd Edition

ISBN:9781285686691

Author:Crouch

Publisher:Crouch

Chapter14: Chromatography

Section: Chapter Questions

Problem 9P

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percentage recovery of benzoic acid is 77.18%. The melting point range of crude benzoic acid = 112-119°C and the melting point range of pure benzoic acid (crystals) = 122-125. Comment on the percentage recovery of benzoic acid. Comment and compare the melting point of the crude and crystal samples
In a chromatographic analysis, a solution containing 0.0837M toluene and 0.0666M xylene resulted in peak areas of Atoluene= 423 and Axylene= 347. To analyze an unknown sample, 10.0mL of 0.146M xylene was added to 10.0mL of an unknown toluene-containing solution, and the mixture was diluted to 25.0mL. This mixture gave a chromatogram with peak areas of Atoluene= 553 and Axylene= 582. What was the concentration of toluene in the unknown solution?
4. (14 points) A soil sample (4.00 g) is digested and analyzed for Cd by atomic absorption analysis. The digestion results in 25.0 mL of extract. Because there is concern of matrix effects, standard addition is used. A portion of the extract is analyzed directly by AA and gives an absorbance of 0.211. Another 10.0 mL portion of the extract is spiked with 50.0 ug of Cd (ignore any added volume from Cd spiking) and gives an absorbance of 0.539. a) Calculate the Cd concentration in the (unspiked) extract (in ug/mL). (8 pts) b) Calculate the Cd concentration in the soil in ppm (by mass). (3 pts) c) A Cd standard prepared in dilute nitric acid to a concentration of 1.00 µg/mL is analyzed and gives an absorbance of 0.191. Was the standard addition justified? (3 pts)
In coulometric karl Fisher water analysis, 25.0 mL of pure “dry” methanol required 4.23 C to generate enough I2 to react with residual H2O in methanol. A suspension of 0.8476 g of finely ground polymeric material in 25.0 mL of the same “dry” methanol required 63.16 C. Find the weight percent of water in the polymer.
The following data give the recovery of bromide from spiked samples of vegetable matter, measuredusing a gas–liquid chromatographic method. The same amount of bromide was added to each specimen(Roughan, J.A., Roughan, P.A. and Wilkins, J.P.G., 1983, Analyst, 108: 742).Tomato: 777 790 759 790 770 758 764 ug/gCucumber: 782 773 778 765 789 797 782 ug/g(a) Test whether the recoveries from the two vegetables have variances which differ significantly.(b) Test whether the mean recovery rates differ significantly.
2. A coal sample analysis on mass basis was reported as C = 76.3%, H2 = 4.2%, O2 = 4.5%, and Moisture = 7%, Mineral matter = 3% and Ash = 5%. Calculate the LCV in Ash, mineral matter free basis of 2lb of coal.
The following results were obtained for the determination of calcium in a NIST limestone sample: %CaO = 50.33, 50.22, 50.36, 50.21, and 50.44. Five gross samples were then obtained for a carload of limestone. The average %CaO values for the gross samples were found to be 49.53, 50.12, 49.60, 49.87, and 50.49. Calculate the relative standard deviation associated with the sampling step
e. In a GC analysis for the determination of limonene in orange peel, separate solutions of 100 ppm limonene standard and 100 ppm propanol internal standard (IS) gave peaks of 1273 and 598 respectively. A sample of the extract (50.0 mL) was spiked with 10.0 mL of 1000 ppm propanol and the mixture diluted to 100 mL. This solution gave peak areas of 723 and 519 for limonene and propanol respectively. What is the concentration of limonene in the extract?
A dilute peroxide solution was prepared by quantitatively diluting 10 mL stock H2O2 (MW = 34.0147) to 250mL using a volumetric flask. 50 mL aliquot of the diluted peroxide solution was titrated using the previously standardized KMnO4 in problem 1. Titration of the sample required 29.00 mL titrant and the blank containing 50 mL 1:5 H2SO4 required 0.75 mL of the standard KMnO4. Calculate the concentration in %w/v of the stock H2O2. (Hint: H2O2 produces O2 under acidic condition). Follow sig. Fig
Introduction for polymer molecular weight determination by dilute solution viscosity measurement.
3. (a) The following are the results from subjecting the lectin to SDS-PAGE: Band / Molecular Length 210 100 67 48 32 Lectin Weight (kDa) of Gel Migration Distance 7.2 1.8 2.5 3.2 3.9 4.7 3.5 (cm) Determine the molecular weight of the lectin. Show all workings.
If 9 grams of polymer A with molecular weight of 30,000 Dalton is mixed with 5 grams of polymer B with molecular weight of 50,000 Dalton, calculate the number average molecular weight, weight average molecular weight and polydispersity index of the polymer mixture.