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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Sis290025 on January 23, 2006, 03:11:08 PM

Title: Absorption Spectrum: What is the best wavelength to work with?
Post by: Sis290025 on January 23, 2006, 03:11:08 PM

The following absorbances were obtained for a solution whose concentration was 0.0120 M. What is the best wavelength to work with this substance and why?

lambda (nm)-----------Absorbance
300----------------------.002
325----------------------.016
350------------------------.144
375------------------------.341
400--------------------------.578
425-------------------------.681
450-------------------------.558
475-------------------------.281
500--------------------------.092
525--------------------------.031
550--------------------------.004
575---------------------------.001

Is the best wavelength 425 because it has a peak there or absorbs the most light?

Thank you.

Title: Re:Absorption Spectrum
Post by: plu on January 23, 2006, 03:29:42 PM

Absolutely.  425 nm would be referred to as lambda_max

Title: Re:Absorption Spectrum: What is the best wavelength to work with?
Post by: mike on January 24, 2006, 08:29:13 PM

as plu stated the lambda max is th most appropriate wavelength to use.

this will give you the best absorbance readings for that concentration. it will also guarantee you absorbance readings at higher concentrations. at lower concentrations you will be able to get more absorbance readings than if you were to use a wavelength either side of the lambda max.