[CHM 112] About Lab

[Andrew J. Pounds]

On 07/14/14 18:11,  wrote:
> Dr. Pounds,
>
> For the Gaseous Equilibrium Lab, I really do not understand why we set the Spectro device to 500nm. The lab report also asked us this but I don’t understand why? Could you explain?
>
> Thank you.

You needed a wavelength  "close" to the maximum absorbance value. You 
then changed the wavelength to see how the absorbance changed with the 
wavelength.   This was all "qualitative".  You then set the wavelength 
to a give a %T of 25 so you could complete the rest of the experiment.

If you had not done that last step, when you heated the sample up (and 
it got darker) you would gotten poor data for the high temperature 
readings.  You needed some "wiggle room" (also known as headroom in the 
linear dynamic range of the detector) so that you didn't get crazy 
values (such as negative percent transmittances or absorbance values 
greater than 2) at the higher temps.





-- 
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