Researcher

Samantha Gaines with Lizzie Clark and Lacie Condron

Objective

To calculate the solubility of trans-cinnamic acid in 2-pentanol by density method. The additivity of volumes is an assumption and the density of the solid is obtained from ChemSpider.

Materials

electronic balance
water bath
25 mL volumetric flask
100 mL beaker
pipette
microspatula
trans-cinnamic acid
2-pentanol
parafilm

Procedure

Use the electronic balance to obtain the mass of the empty 25 mL volumetric flask. Pipette 25 mL of pure 2-pentanol solvent into the volumetric flask and weigh, subtracting the mass of the empty volumetric flask. Record room temperature, mass, and volume. Decant solvent from volumetric flask into 100 mL beaker. Add approximately 10 mL of excess solvent to the 100 mL beaker. Add 133% of the predicted trans-cinnamic acid needed for a saturated solution to the 2-pentanol. See calculations here. Heat the solution in a 45 C water bath until the trans-cinnamic acid dissolves. Cool the water bath to 25 C and wait for the precipitate to come out of the solution. Obtain the mass of the empty 25 mL volumetric flask using an electronic balance. When precipitate crystals form, pipette 25 mL of the supernatent into the volumetric flask. Weigh the solution with an electronic balance, subtracting the mass of the empty volumetric flask from that of the flask and solution. Record mass, room temperature, and volume. Enter all data into the "results" spreadsheet.

Results

Measured solubility of trans-cinnamic acid in 2-pentanol.

Discussion

The observed density of 2-pentanol was 0.8100 g/mL. The observed density of the supernatent of the saturated solution of trans-cinnamic acid and 2-pentanol was 0.8452 g/mL. From this, the concentration of trans-cinnamic acid in a saturated solution was calculated to be 0.6788 M. The predicted solubility of trans-cinnamic acid in 2-pentanol is 0.560 M. The solubility measured in this experiment was 0.1188 M higher than the predicted value.

Conclusion

The measured solubility of trans-cinnamic acid in 2-pentanol was approximately 0.6788 M.

Log

2011-11-28
9:14 Weighed empty 25 mL volumetric flask: 20.0432g
9:16 Weighed flask plus 25 mL of 2-pentanol: 40.2936g
9:20 Poured liquid into 100 mL beaker and added more 2-pentanol, to approximately 35 mL.
9:22 Weighed out 5.1772g of trans-cinnamic acid.
9:24 Added cinnamic acid to solvent in beaker and parafilmed.
9:35 placed beaker in 45C water bath.
9:39 All solute had dissolved, solution clear (yellow). Placed beaker in 25C water bath.
10:10 There was no precipatate. Removed parafilm to allow some solvent to evaporate in order to induce more saturated solution and crystal formation.
10:42 Precipitate formed crystals at 24.3 C.
10:43 Measured weight of empty volumetric flask using electric balance at room temperature of 19.9 C. Flask weighed 20.0687 g.
10:52 Pipetted 25 mL of supernatent into flask at 23.8 C.
10:59 Parafilmed flask.
11:09 Removed parafilm and weighed flask containing supernatent using the same balance at 19.0 C. Flask and supernatent weighed 41.1996 g.