Analytical Chem istry - DePauw University

Chapter 8 Gravimetric Methods403and that one molecule of H 2 O forms two surface hydroxyls, calculatethe density of surface hydroxyls in mmol/m 2 .35. The concentration of airborne particulates in an industrial workplacewas determined by pulling the air through a single-stage air samplerequipped with a glass-fiber filter. The air was sampled for 20 min ata rate of 75 m 3 /h. At the end of the sampling period, the filter’s masswas found to have increased by 345.2 mg. What is the concentrationof particulates in the air sample in mg/m 3 and mg/L?36. The fat content of potato chips is determined indirectly by weighing asample before and after extracting the fat with supercritical CO 2 . Thefollowing data were obtained for the analysis of potato chips. 16Sample Number Initial Mass (g) Final Mass (g)1 1.1661 0.92532 1.1723 0.92523 1.2525 0.98504 1.2280 0.95625 1.2837 1.0119(a) Determine the mean and standard deviation for the %w/w fat.(b) This sample of potato chips is known to have a fat content of 22.7%w/w. Is there any evidence for a determinate error at a = 0.05? Seethe appendices for statistical tables.37. Delumyea and McCleary reported results for the %w/w organic materialin sediment samples collected at different depths from a cove on theSt. Johns River in Jacksonville, FL. 17 After collecting a sediment core,they sectioned it into 2-cm increments. Each increment was treatedusing the following procedure:(a) The sediment was placed in 50 mL of deionized water and the resultingslurry filtered through preweighed filter paper;(b) The filter paper and the sediment were placed in a preweighed evaporatingdish and dried to a constant weight in an oven at 110 o C;(c) The evaporating dish containing the filter paper and the sedimentwere transferred to a muffle furnace where the filter paper and anyorganic material in the sample were removed by ashing;(d) Finally, the inorganic residue remaining after ashing was weighed.Using the following data, determine the %w/w organic material as afunction of the average depth for each increment.16 Fat Determination by SFE, ISCO, Inc. Lincoln, NE.17 Delumyea, R. D.; McCleary, D. L. J. Chem. Educ. 1993, 70, 172–173.