Distribution Equilibrium

A-Level: Chemistry

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Objective
To determine the distribution (partition) coefficient for the equilibrium that exists when NH3 is distributed between water & ether.
Principle
By shaking ammonia solution solution with diethyl ether, the concentration of NH3 in each solvent is determined by titration. The partition coefficient, Kd, can be obtained due to different solubility of solute in 2 solvents.



Chemicals
0.010 & 0.50M HCl, diethyl ether, 1M NH3, methyl orange indicator
Apparatus
titration apparatus, separating funnel, 10ml pipettes, beakers, measuring cylinders
Procedure
1.> Pour about 50 cm3 of NH3 solution into a separating funnel.
2.> Pour about 50 cm3 of diethyl ether into same separating funnel.
3.> Holding the tap firmly in position with one hand and the stopper with another, shake the separating funnel vigorously for about 10 seconds.
Release the pressure inside by loosen the tap for a moment. Continue shaking for about 2 minutes, releasing the pressure every 10 seconds. Set
aside until 2 layers separate.
4.> Transfer the lower aqueous layer to a beaker. Pipette 10 cm3 to a conical flask, add about 20 cm3 of deionized water and a few drops of methyl
orange and titrates with 0.50M HCl. (Remember to remove the stopper before running the solution)
5.> Titrates 2 - 3 more 10 cm3 samples and completes Table 1.
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