To Determination the Partition Coefficient of Ethanoic Acid Between Water and Butan-2-Ol

Aim

To determination the partition coefficient of ethanoic acid between water and butan-2-ol.

Procedure

1. The room temperature was recorded.

2. 15cm3 of the given aqueous ethanoic acid and 15cm3 of butan-2-ol were poured into a 100cm3 separating funnel, using suitable apparatus. The funnel was stoppered and was shook vigorously for 1 to 2 minutes. (The pressure in the funnel was released by occasionally opening the tap.)

3. 10cm3 of each layer was separated approximately. (The fraction near the junction of the two layers was discarded.)

4. 10.0cm3 of the aqueous layer was pipetted into a conical flask and was titrated with 0.1 M sodium hydroxide solution using phenolphthalein.

5. Using another pipette, 10.0 cm3 of the alcohol layer was delivered into a conical flask and was titrated with 0.1 M sodium hydroxide solution.

6. Steps (2) to (5) was repeated with another separating funnel using the following volume:

25cm3 of aqueous ethanoic acid and 15cm3 of butan-2-ol

7. For each experiment, the ratio of the concentration of ethanoic acid in the aqueous layer to that in the butan-2-ol layer was calculated.

Result

Room temperature: 29?

Volume of butan-2-ol: 15 cm3

Volume of 0.2M ethanoic acid / cm3 Volume of 0.1M NaOH titre for aqueous layer / cm3 Volume of 0.1M NaOH titre for alcohol layer / cm3 Partition coefficient

K=conc. of acid in aq. layerconc . of acid in alc. layer

15 10.00 12.55 0.796

25 12.10 15.60 0.776

Conclusion

The partition coefficient of ethanoic acid between water and butan-2-ol is :

=0.796 + 0.7762

=0.786

Discussion

1. Shaking is necessary in step (2) because it made it faster to attain equilibrium state.

2. When temperature increases, the solubility of the two solvents increase. But the rate of the increase in solubility are not the same, it is expected that the partition coefficient varies with temperature.

3. The aim of titration is to find the concentration of the solvent, but not the total number of mole in the solvent.