The selenium content in soil can be determined fluorometrically upon conversion of the selenium to the fluorescent product shown, followed by extraction in cyclohexane. Emission from the fluorescent product is observed at 518 nm. The selenium content in a 0.168 g soil sample was converted to the fluorescent product and extracted in 50.0 mL of cyclohexane. The method of standard additions was used to determine the selenium content in the soil sample. Initially, 3.00 mL of the cyclohexane solution were placed in a cuvette for fluorescence determination. Several small additions of a 2.49 µg Se/mL. standard solution containing the fluorescent product were added to the 3.00 ml. solution in the cuvette. The fluorescence was measured at 518 nm. The results are shown in the table. Total added Se standard volume (µL) 0.00 20.0 40.0 60.0 80.0 Fluorescence intensity (arbitrary units) 54.3 64.5 76.7 91.1 108.3 Se Determine the weight percent (wt%) of selenium in the soil sample and find the absolute uncertainty in the weight percent of selenium. Report the weight percent and absolute uncertainty with three significant figures.

The selenium content in soil can be determined fluorometrically upon conversion of the selenium to the fluorescent product shown, followed by extraction in cyclohexane. Emission from the fluorescent product is observed at 518 nm. The selenium content in a 0.168 g soil sample was converted to the fluorescent product and extracted in 50.0 mL of cyclohexane. The method of standard additions was used to determine the selenium content in the soil sample. Initially, 3.00 mL of the cyclohexane solution were placed in a cuvette for fluorescence determination. Several small additions of a 2.49 µg Se/mL. standard solution containing the fluorescent product were added to the 3.00 ml. solution in the cuvette. The fluorescence was measured at 518 nm. The results are shown in the table. Total added Se standard volume (µL) 0.00 20.0 40.0 60.0 80.0 Fluorescence intensity (arbitrary units) 54.3 64.5 76.7 91.1 108.3 Se Determine the weight percent (wt%) of selenium in the soil sample and find the absolute uncertainty in the weight percent of selenium. Report the weight percent and absolute uncertainty with three significant figures.

Chemistry: Principles and Practice

3rd Edition

ISBN:9780534420123

Author:Daniel L. Reger, Scott R. Goode, David W. Ball, Edward Mercer

Publisher:Daniel L. Reger, Scott R. Goode, David W. Ball, Edward Mercer

Chapter18: Electrochemistry

Section: Chapter Questions

Problem 18.104QE

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