Researchers

Lacey Condron with Lizzie Clark and Andrew Lang

Objective

To determine the solubility of Palmitic acid in 1-butanol using the density method. The additivity of volumes is an assumption and the density of the solute is obtained from ChemSpider.

Procedure

1-butanol solution was obtained, volumetric flask was weighed (20.252 g) and the weight of 25 ml of 1-butanol solution (20.248 g) was obtained from the electronic balance. Contents of the flask were transferred to a 100 mL beaker. An excess amount of solvent was added to the 100 mL beaker making approximately 30 mL of solvent. The amount of Palmitic acid was previously calculated using the predicted value plus 10%-Planning Sheet. Palmitic acid (2.157 g) was added using a microspatula; this procedure was done in a room with a measured temperature at 19.5 degrees C. After the Palmitic acid was added, the beaker was covered with parafilm to avoid spilling, contamination and vaporization of the liquid.The beaker was placed in a hot water bath (tap water) at 48 degrees C to allow the solute to fully dissolve.The beaker was swirled periodically to assist in dissolving the solute. After the Palmitic acid was all dissolved, the beaker was placed in a 25.0 degrees C water bath. The beaker remained in this water bath for approximately 40 minutes and still, no crystals had formed. The beaker was removed from the water bath and was placed in an environment of 20 degree C. After approximately 20 minutes at this temperature, still no crystals had formed. Because no crystals had formed, Palmitic acid was added again (1.040 g). The beaker was put into a 45 degree C water bath to allow the solute to dissolve. Once fully dissolved, the beaker was placed in a 25 degree C water bath. This allowed the beaker to cool and begin to form crystals.Still, no precipitate formed. Another 1.125 g of Palmitic acid was added to the beaker. The beaker was placed in a 45 degree C water bath to dissolve the remaining Palmitic acid. After approximately 35 minutes crystals began forming in the beaker. The flask was weighed (20.255 g) at 19.5 degrees C. 25 mL of the supernatant liquid was pipetted into the 25 mL volumetric flask. The weight of the volumetric flask and supernatant was obtained (40.697 g). More crystals formed on the bottom of the volumetric flask which was a result of the solution being slightly cooled when being transferred from the 25.0 degree C water bath, to the balance.

Results

The concentration of Palmitic Acid in 1-butanol at 25 degrees C was measured to be 0.600 M.
Calculation Spreadsheet

Log

9:20 Weighed of 25mL volumetric flask- 20.252 g
9:23 Pipetted 25mL of 1-butanol into the previously weighed volumetric flask. Weighed 25mL of 1-butanol- 20.248 g
9:24 Poured the previously weighed 25mL of 1-butanol into 100mL beaker along with 10mL extra of solvent.
9:26 Weighed/ added Palmitic acid (2.157 g) at 19.5 degrees C.
9:28 Placed beaker in 48 degree C water bath using tap water.
9:29 Beakers were continuously swirled to assist in the dissolving process while the temperature of the water bath was maintained to stay within 45-50 degrees C.
9:32 All Palmitic acid is dissolved, beaker was placed in a 25.0 degrees C water bath that was created using a hot plate. All of this was done under a fume hood.
10:10 Still no precipitate formed in the 25 degree C water bath so the beaker was moved to a 20 degree C room to try to get it to form crystals.
10:30 Still no crystals were formed so another 1.040 g of Palmitic acid was added to the 100 mL beaker and swirled to dissolve.
10:40 The beaker was placed back into a 25 degree C water bath under the fume hood.
10:52 Still no precipitate formed, the beaker was removed from the 25 degree C water bath and placed in a 20.0 degree C environment.
10:57 Another 1.125 g of Palmitic acid was added to the beaker. The beaker was parafilmed and placed in a 45 degree C water bath until all solute dissolved. The beaker was then placed in a 25C water bath.
11:33 Crystals had formed in the bottom of the beaker 25C. Weight of empty 25mL volumetric flask 20.255g
11:36 Decanted and weighed 25 mL of supernatant. Weight of flask plus contents was 40.697g