Molar absoiptivity

The spreadsheet below shows some of the data. You will need to use all the data. Column A contains [mesitylene] and column B contains [I2]tot. Column C lists the measured absorbance. Guess a value of the molar absoiptivity of the complex, e, in cell A7. Then compute the concentration of the complex (= Ale) in column D. The equilibrium constant in column E is given by E2 = [complex]/ ([I2J [mesitylene]) = (D2)/((B2-D2) A2). 

If this absorbance were measured, the molar absoiption coefficient inferred from it without consideration of the dimerization would be... 

Molar absoiptivities in the range of 5000 to 30,000 are typical for the tt —> ir transitions of conjugated polyene systems. Such large molar absoiptivities are helpful, since spectra may be obtained with veiy small amounts of sample. On the other hand, samples and solvents for UV spectroscopy must be extremely pure. A minute impurity with a large molar absoiptivity can easily obscure the spectrum of the desired compound. 

To analyze 1,2-ethanediol, oxidation with excess IO4 is followed by passage of the reaction solution through an anion-exchange resin that binds both IO4 and IO3. lO is then quantitatively removed from the resin by elution with NH4CI. The absorbance of eluate is measured at 232 nm to find the quantity of 10 J (molar absoiptivity (e) = 9(X) M cm ) produced by the reaction. In one experiment, 0.213 9 g of aqueous 1,2-ethanediol was dissolved in 10.(X) mL. Then 1.000 mL of the solution was treated with 3 mL of 0.15 M KIO4 and subjected to ion-exchange... 

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