Chapter 17-18: Spectrophotometry ectroscopy – the interaction of radiation and matte Spectroscopic methods measure the amt of radiation produced or absorbed Elucidation of molecular structure Qual./Quant. Detn. of inorganic and organic compds Classif y Region of the electromagnetic spectrum X-ray UV Visible IR
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Chapter 17-18: Spectrophotometry
Spectroscopy – the interaction of radiation and matter
Spectroscopic methods measure the amt of radiation produced or absorbedElucidation of molecular structureQual./Quant. Detn. of inorganic and organic compds
Classify
Region of the electromagnetic spectrumX-rayUVVisibleIR
Electromagnetic radiation – as a wave
Waves – properties of wavelength, frequency, velocity, amplitude
Particles – discrete packets of energy called photons
Quantitative Chemical AnalysisF = kC (at constant P0)Linear at low concentrations
Why drop in I ?
A compound with a molecular weight of 125.0 has a molar absorptivity of 2.5 x 105 M-1cm-1. How many grams of thiscompound should be dissolved in 1.00 L such that after a 200-fold dilution the resulting solution will give an absorbanceof 0.60 in a 1.0 cm cell
Clicker question
Cytochrome c has a molar absorptivity of 106,000 M-1cm-1. 100 uL of a solution cyt. C is diluted to 1.00 mL. The Absorbance of the diluted solution is 0.30 in a 1.0 mm cell. Calculate the concentration of cyt. C in the original soln.
A 2.00 mL specimen was treated with reagents togenerate color with phosphate following which thesample was diluted to 100.0 mL. Photometric measurement for the phosphate in a 25.0 mL aliquot yielded an absorbance of 0.428. Addition of 1.00mL of a solution containing 0.0500 mg of phosphateto a second 25.0 mL aliquot resulted in an absorbanceof 0.517. Calculate the mgs of phosphate in each milliliter of the specimen.
Clicker question
Quinine in a 1.664 g antimalarial tablet was dissolved insufficient 0.10 M HCL to give 500.0 mL of solution. A 15.00 mL aliquot was then diluted to 100.0 mL with the acid. Thefluorescent intensity for the diluted sample at 347 nm provideda reading of 288 on an arbitrary scale. A standard 100.0-ppmQuinine solution registered 180 when measured under identical conditions. Calculate the mgs of quinine in the tablet