A red-colored complex PbX4 prepared from Pb with ligand X() shows promise as a means to determine trace levels of lead in the environment. The analyst prepares five standard solutions (A, B, C, D, and E) of PB: 30, 60, 90, 120, and 150 ppm, respectively. 5 ml of each solution is mixed with 5 ml of 0.10 M X. The transmittance of the five prepared solutions is measured in a 1 cm cell. A reagent blank (5 mL of distilled water and 5 mL of 0.10 M X) is used to set T = 1.00. The transmittances of the resultant solutions are 0.717, 0.543, 0.466, 0.384, and 0.259 for solutions A, B, C, D, and E, respectively.
What is the molar absorptivity (in 4 or more significant digits) of the complex?
(Assume all Pb is complexed into PbX4)© BrainMass Inc. brainmass.com October 24, 2018, 5:28 pm ad1c9bdddf
To answer this question we must look at the theory behind absorption spectroscopy. The absorption of any solute in a solution is dependant on three variables: (a) the molar extinction coefficient (molar absorptivity), (b) the path length (usually 1 cm) and (c) the concentration (in ...
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One knows that the Beer-Lambert law, expresses the relationship of the spectrophotometric absorbance (Abs) of a solution of a compound to the concentration(c) and light path length (l) of the sample. The proportionality constant, when the solution concentration is in M, is called the molar extinction coefficient (E). One would like to determine the molar extinction coefficient (E) of a "newly discovered compound". One places 3.00 mL of a solution that is 5.37 x 10^-6 M in a 1 cm^2 cuvette. The absorbance that one measures is .863. What is the extinction coefficient? And just to be sure what are the units of the molar extinction coefficient (E)?
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