[CHM 111] lab question

[Andrew J. Pounds]

On 11/18/2015 03:37 PM,  wrote:
> Dr. Pounds
>
> What value do we use for the epsilon variable in Beers' law formula (A 
> = c × l × e)? Is it 262.9?
>
> Thanks
>
Whoa!  No.

You have calculated the concentration (c) and you measured the 
absorbance (A).  Beer's law simply shows us that there is a linear 
relationship between concentration and absorbance.   Therefore you plot 
the absorbance on the Y-axis and the concetration on the X-axis and fit 
a line to that.  The path length and epsilon are tied up in the "slope", 
but they are irrelevant for the calculations you are doing.

I have placed a sample plot on the class website.


You use the molar mass of the nickel sulfate hexahydrate (what I think 
is your 262.9 number above) when calculating the concentrations.

Keep the questions coming if you have them.


-- 
Andrew J. Pounds, Ph.D.  (pounds_aj at mercer.edu)
Professor of Chemistry and Computer Science
Mercer University,  Macon, GA 31207   (478) 301-5627
http://faculty.mercer.edu/pounds_aj

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