Chemical Forums
Chemistry Forums for Students => Inorganic Chemistry Forum => Topic started by: integral0 on April 01, 2005, 01:15:56 PM
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7. The absorbances at a particular wavelength of a set of known concentration solutions was measured on a spectronic 20. A plot of concentration vs. absorbance gave a slope of 2.100 x 10-4 and an intercept of approximately zero. What is the value of the molar extinction coefficient (molar absorbivity, E) at the wavelength?
a. 2.128 x 10-4
b. 6120
c. 2.100x10-4
d. 4762
e. 4700
The answer is "a"
I have no clue how to solve it.... ???
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Hello Integral0,
It appears that there is insufficient information to derive a reasonable conclusion. Here are a few questions that I have:
1) What is the intercept if it is approximately zero (is an actual value provided?)
2) What are the molar concentration measured?
The reason why I ask these questions are:
1) given: A/E= molar concentration, if the molar concentration is 1.0 at the given absorbance, then the calculated value is 2.100x10-4. If you are given a different molar concentration, then this would change the value.
2) if the intercept is not zero, this will change the slope value (it could explain the difference between 2.128x10-4 and 2.100x10-4)
I hope this helps,
Eugene Dakin Ph.D., P.Chem.