Subject: Chemistry TAS Experiment13 msn: Name: Eric LI [18/5/2007]
Determination of the distribution coef. of ethanoic acid between water and 2-methylpropan-1-ol
Aim
To determine the distribution (partition) coefficient for the equilibrium that exists when ethanoic acid is distributed between water and 2-methylpropan-1-ol.
Principle
By shaking ethanoic acid solution with 2-methylpropan-1-ol, the concentration of ethanoic acid in each solvent is determined by titration. The partition coefficient, Kd, can be obtained due to different solubility of solute in 2 solvents.
Apparatus
titration apparatus, separating funnel, 10ml pipettes, beakers, measuring cylinders
Procedure
- 15cm3 of the given aqueous ethanoic acid and 25cm3 of 2-methylpropan-1-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.)
- 10cm3 of each layer was separated approximately. (The fraction near the junction of the two layers was discarded.)
- 10.0cm3 of the aqueous layer was pipetted into a conical flask and was titrated with 0.1 M sodium hydroxide solution using phenolphthalein.
- 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.
- Steps (1) to (4) was repeated with another separating funnel using the following volume: