EXP 264

Researcher

Ashley Sweeney with Samantha Gaines [Nice work. Remove all the span tags from the WikiText -AL]

Objective

To determine the solubility of Palmitic acid in 2-pentanol using the density method. The additivity of volumes is an assumption and the density of the solute is obtained from ChemSpider.

Procedure

2-pentanol solution was obtained, volumetric flask was weighed (20.045 g) and the weight of 25 ml of 1-butanol solution (20.235 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. The amount seemed excessive so about half the amount was initially added. Palmitic acid (10.058 g) was added using a microspatula; this procedure was done in a room with a measured temperature at 20 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 45 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 an environment of 20 degree C. After approximately 10 minutes at this temperature, crystals began forming. After 28 minutes at this temperature, the solution had turned to slush. 20 mL of 2-pentanol was added to the beaker. The beaker was placed in a hot water bath (tap water) at 45 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 an environment of 20 degree C. After approximately 19 minutes at this temperature, crystals began forming. After 38 minutes at this temperature, the solution had turned to slush. 10 mL of 2-pentanol was added to the beaker. The beaker again was placed in a hot water bath at 45 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 again was placed in an environment of 20 degree C. After approximately 14 minutes at this temperature, crystals began forming. After 11 minutes at this temperature, the solution had turned to slush. 10 mL of 2-pentanol was added to the beaker. The beaker was placed in a hot water bath (tap water) at 45 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 an environment of 20 degree C. After approximately 35 minutes at this temperature, crystals began forming. After 43 minutes at this temperature, no continuing crystal formation was seen.
The flask was weighed (22.593 g) at 20 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 (43.089 g).

Results

The concentration of Palmitic Acid in 2-pentanol at 20 degrees C was measured to be 0.797 M.
Calculation Spreadsheet


Log

1416 Weighed 25-mL volumetric flask- 20.045 g.
1438 Pipetted 25 mL of 2-pentanol into the previously weighed volumetric flask. Weighed 25 mL of 2-pentanol- 20.235 g.
1439 Poured the previously weighed 25 mL of 2-pentanol into 100mL beaker along with 5 mL extra of solvent.
1442 Weighted/added Palmitic acid (10.058 g) at 20 degrees C.
1450 Placed beaker in 45 degree C (tap) water bath.
1450
Beaker was continuously swirled to assist in the dissolving process while the temperature of the water bath was maintained to stay within 45-50 degrees C.
1506 Replaced parafilm cover on beaker.
1510
All Palmitic acid is dissolved, beaker was placed in a 20 degree C environment.
1520 Crystals had formed in the bottom of the beaker at 20 degree C.
1538 Solution had turned to slush.
1538 20 mL of 2-pentanol added to beaker.
1539
Placed beaker in 45 degree C water bath.
1543 All Palmitic acid is dissolved, beaker was placed in a 20 degree C environment.
1602 Crystals had formed in the bottom of the beaker at 20 degree C.
1619 Weight of empty 25mL volumetric flask and stopper- 22.593g.
1620 Solution had turned to slush.
1621 10 mL of 2 pentanol added to beaker.
1621 Placed beaker in 45 degree C water bath.
1623
All Palmitic acid is dissolved, beaker was placed in a 20 degree C environment.
1637 Crystals had formed in the bottom of the beaker at 20 degree C.
1647 Solution had turned to slush.
1648 10 mL of 2-pentanol added to beaker.
1650
All Palmitic acid is dissolved, beaker was placed in a 20 degree C environment.
1725 Crystals had formed in the bottom of the beaker at 20 degree C.
1733 No continuing crystal formation seen. The solution was decanted and 25 mL of the supernatant was weight. The weight of the flask plus the contents was 43.089