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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: mandytan on December 06, 2011, 11:09:11 AM

Title: UV spectrum
Post by: mandytan on December 06, 2011, 11:09:11 AM

0.2g of a solid is dissolved in 1L solvent to give a concentration of  0.2g/L.
UV absorbance spectrum was collected.
The solid has 0.1%w/w water content.
What is the formula to calculate the absorptivity on the dried basis? 

Title: Re: UV spectrum
Post by: Arkcon on December 06, 2011, 01:02:15 PM

Well, start with the simplest part.  If you mass out 0.2 g of something, and you know it is 0.1 % w/w water, how much did you really add?

Title: Re: UV spectrum
Post by: mandytan on December 06, 2011, 04:15:24 PM

So it means I actually added 0.1998g (dried substance).when we calculate absorptivity, do we use the concentration in g/L or mol/L?

Title: Re: UV spectrum
Post by: Arkcon on December 06, 2011, 04:28:48 PM

Well, the only info we have so far is grams per liter.  If you have the molar mass, you can convert, depending on what final answer you want.