Limitations

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General Concepts

A solute compound, adipic acid, is dissolved in water. The aqueous solution is referred to as the stock solution. 30.0 mL portions of it are extracted with diethyl ether.   Some of the adipic acid will migrate into the ether layer and some will remain in the water.

The distribution coefficient, K_D, is the ratio of the concentration of the adipic acid in the organic layer to the concentration in the aqueous layer. A concentration is a ratio of quantity of solute to volume of solution. The volumes of the organic and aqueous layers are known by measurement.    The quantity of the adipic acid present in an aqueous layer is expressed as the volume of an NaOH solution necessary to titrate the adipic acid in the aqueous layer.  The quantity in the organic layer is the difference between the volumes of NaOH needed for titration of the stock solution without extraction and the volume after extraction.

The Calculation page will help you with some of these calculations. Make sure to answer the questions posed to you on that page.

Experimental Techniques

Care should be paid to estimate the volumes to 0.02 mL. Volumes of the stock solution and ether should be measured out with similar accuracy using a small graduated cylinder. Titrations should be repeated until the spread in values required for neutralization is less than 0.2 mL. Significant figures should be evaluated and data entered into the calculation sheets accordingly.

1. 30 mL portions of the stock solution are titrated with a NaOH solution.  This series of titrations allows the determination of the adipic acid concentration (relative to the NaOH concentration).
2. 30 mL portions of the stock solution are extracted with 30 mL volumes of ether and the aqueous layer is titrated.  This series of titrations allows you to determine how much of the  adipic acid has left the aqueous layer and migrated into the ether layer. K_D is calculated.
3. 30 mL portions of the stock solution are extracted with two 15 mL portions of ether and how much adipic acid remains in the aqueous layer is determined.

Printing of Results

Printing of tables, etc. from the Calculations page is best done by right clicking the portion of the page you desire to print and then selecting Print.