Partition Coefficient: Extraction of Benzanoic Acid

Tyler Harmon

10/23/14

Instructor: Michelle Young

The Partition Coefficient: Extraction of Benzoic Acid

Abstract:

The purpose of this lab was to extract benzoic acid from two immiscible phases and calculate the partition coefficient of each. Benzoic acid is a hydrophobic compound, so it is only slightly soluble in water. On the other hand, it is very soluble in a compound such as methylene chloride. Because of this, benzoic acid will have a lower partition coefficient in methylene chloride because much more of it will dissolve than in water.

Chemical Structures:

Procedure:

I used the procedure on page 22 of the lab manual entitled “Solubility, Solvent Extraction (The Partition Coefficient).” No changes or deviations were made to the procedure.

Data:

| Original Mass of Benzoic Acid | Recovered Mass of Benzoic Acid | Partition Coefficient |

Part A | 55mg | 49mg | 8.167 |

Part B | 54mg | 16mg | 0.4211 |

Culture Tube A | Empty – 11,307mg With Solid – 11,356mg |

Culture Tube B | Empty – 11,445mg With Solid – 11,461mg |

Calculations:

Kp = mg Organic layer (recovered) / mg Aqueous layer

Aqueous layer = original mass – recovered mass

Part A

Aqueous Layer: 55mg – 49mg = 6mg Aqueous

Kpa = 49mg / 6mg Kpa = 8.167

Part B

Aqueous Layer: 54mg – 16mg = 38mg

Kpb = 16mg / 38mg Kpb = 0.4211

Conclusions:

The goal of this lab was to extract benzoic acid from two immiscible phases. In Part A, benzoic acid, which is a hydrophobic compound, was slightly dissolved in deionized water. In Part B, benzoic acid was mostly dissolved into Sodium Bicarbonate. Methylene Chloride was used as a constant in both parts. I calculated the Partition Coefficients to be 8.167 and 0.4211 for Parts A and B respectively. Part B has such a low partition coefficient because most of the benzoic acid was dissolved and very little was recovered as a solid. On the other hand, Part A has such a high partition coefficient because most of the...