spirocycle
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data question
In a lab demonstrating the effect of EWG to the rate of chromic acid oxidation, our lab instructor had us use a UV spectrophotometer to measure the
absorbance of the reaction mixture (at the wavelength that corresponds to chromic acid color) over time
We recorded once each minute (t= 0, 1,2,3,4,5,6) and t=66 (which we treated at t infinite).
When graphing the data, we used the x axis as time (duh) and the y axis as ln[(Ao-Ainf)/(At-Ainf)]
my question is: what does that value correspond to?
It is clear that the absorbance is related to concentration of chromate.
so here is my reasoning so far:
Ao-Ainf represents the total change in Absorbance
At-Ainf represents the net displacement of absorbance from the infinite point
I am essentially recording the negative ln of the ratio of the two
edit: issue resolved.
We are finding the difference in ln(absorbance differences) expressed as a single value to give the change in [dichromate].
I guess this means that ln[dichromate] (or something close) is used in determining the absorbance of the solution
[Edited on 7-2-2011 by spirocycle]
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entropy51
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I think that you are using Beer-Lambert Law, which is why you are using the negative log of absorbance.
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spirocycle
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Yea I asked before I read the details fully
thanks
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