[include image of solute JCB]

Researcher

Evan Curtin and Ha Pham

Objective

To calculate the solubility of (trans) - cinnamic acid in methanol and ethanol by density method. The additivity of volumes is an assumption and the density of the solid is obtained from ChemSpider prediction.(1.184 g/mL)

Procedure

Made-up a mixture of cinnamic acid in methanol (sample 1) and a mixture of cinnamic acid in ethanol (sample 2). Place those samples in a hot water bath (41 degree C - no higher than 44 degree C). When the samples were mostly dissolved, removed them from the hot water bath. Immediately, decant the supernatant. Let the decanted supernatant cool down. Observed the formation of any precipitation. Immediately decanted the supernatant and then transferred to volumetric flasks. Weighed out the flasks. Calculated the molarity of the concentrated solution from obtained information.

Results

**Google Spreadsheet - Exp208-1**
The molarity of a solution of methanol saturated with cinnamic acid was found to be:
For the 1mL volumetric flask: 1.432 M
For the 2mL volumetric flask: 1.560 M

The molarity of a solution of ethanol saturated with cinnamic acid was found to be:
For the 1mL volumetric flask: 1.082 M
For the 2mL volumetric flask: 0.802 M

[please add your results to the solsum sheet JCB] (For some reason, I can only view the sheet but not be able to edit it.)

Discussion

Previously measured solubility of cinnamic acid in methanol had a range of 1.3 M - 1.524 M. The range in this experiment was 1.432 M -1.560 M. The average solubility in the database is currently 1.43M, consistent with the 1.432M determined in this experiment.

Previously measured solubility of cinnamic acid in ethanol was 1.03M. The range in this experiment was 0.802 M - 1.082 M. As a result of that, the measured solubility of cinnamic acid in ethanol now had a range of 0.802 M -1.082 M. The average value would be 0.971 M, mean value would be 0.113, and 0.149 would be the standard deviation.

Conclusion

The density method was successfully performed!

References

Solubility of cinnamic acid in methanol
Solubility of cinnamic acid in ethanol

Log

2011-04-01
11:00 - Weighed dry clean 1mL and 2mL volumetric flasks.
11:02 - Added methanol to the 1mL volumetric flask and then weighed the flask now contained 1mL methanol.
11:05 - Repeated the above step with the 2 mL volumetric flask.
11:20 - Set water bath temperature to 40 degree C
11:23 - Added cinnamic acid to the three separate (dry clean) one-dram vials with screw caps such that 2/3 of each tub was fully filled. These three vials were named as sample 1 A, B, and C.
11:25 - Added methanol to each of the three tubs while leaving space (about 0.3 cm from the top).
11:37 - Obtained hot water bath temperature: 41 degree C
11:40 - Submerged 1 A, B, and C in the hot water bath
12:05 - Made up a mixture of 1.04g cinnamic acid and 5 full pipettes of ethanol. This mixture was contained in a 5 dram vial - Sample 2.
12:09 - Obtained the temperature of hot water bath: 43 degree C.
12:10 - Placed sample 2 in the hot water bath such that the level of hot water outside the tub was the same as the level of the mixture inside.
12:12 - Removed sample 2 from the water bath.
12:14 - Removed 1 A, B, and C from water bath. Immediately decanted the supernatant into a 5 dram vial - Sample 1. Covered the vial by a cap then set on the table to cool.
12:16 - Used house air to speed up the evaporation of ethanol solution in sample 2. Precipitation formed after 1 minute!
12:20 - Let sample 2 stand on table to cool.
12:25 - Measured the temperature in sample 2 with a clean dry thermometer: 21 degree C (the same as the room temperature at the time).
12:30 - Removed Sample 1 cap. Could clearly see precipitation remained at the vial bottom.
12:31 - Used a pipette to transfer the supernatant from sample 1 to a dry clean 2mL volumetric flask. Immediately covered the flask with a cap. Did not obtain the temperature of sample 1 at the time (should have done so!)
12:35 - Weighed the 2mL volumetric flask now contained the concentrated solution from sample 1.
12:36 - Another part of the supernatant was transferred from sample 1 to a dry clean 1mL volumetric flask. Immediately covered the flask with a cap.
12:40 - Weighed the 1mL flask contained the concentrated solution.

2011-04-11
11:20 - Weighed out clean dry 2mL and 1mL volumetric flasks.
11:21 - Added ethanol to the flasks and then obtained theirs weight.
11:25 - Cleaned and dried the two flasks before having transferred the supernatant from sample 2 into those.
11:35 - Obtained the weight of flasks now contained concentrated solution from sample 2.