Researcher

Stephanie Costa

Objective

To determine the solubility of cinnamic acid in methanol using the density method. The additivity of the volumes is assumptive

Procedure


Cinnamic acid was dissolved in methanol in a 100C bath. The solution was then cooled to 2C in order to form precipitate. The solubility of cinnamic acid was found using the density method.

Results

Density Sheet 1

Calculations sheet

Precipitate was not formed at 25C. The test tube was in the room temperature bath for 41 minutes. Precipitate was formed when solution was placed in an ice bath. The resulting supernatant was taken off and the density was calculated to be 0.8345 g/mL. The molar concentration at 2C was found to be 1.148 M.

Conversion from 2C to 25C. Converting from 2C to 25C estimates 1.849M. This is significantly higher than other molar concentrations.

Precipitate did not form at 25C because there was not enough solute in the solution (3.0318 g of cinnamic acid was added to about 10mL of methanol). When the temperature was reduced to 2C, precipitate formed and the supernatant was removed to determine the density. The concentration calculated from the densities (see density sheet link) was 1.148 M. Therefore, the solubility of cinnamic acid in methanol at 2C was 1.148 M.

Picture 1
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Sample in the hot water bath


Discussion

At 2C, the concentration was measured to be 1.148M. Precipitate was not visible at 25C, so the temperature of the bath was decreased in order to form precipitate.

The solubility was found to be 1.148M at 2C. In comparison, the existing measured solubility was 1.409 M at around 25C. The resulting concentration found in this experiment did not concurred with the average of other experiments testing the solubility of cinnamic acid in methanol due to the temperature difference. The temperature predictor predicted a solubility of 1.849M at 2C, which is also greater than the solubility measured in this experiment. [This contradicts what you wrote in the Results section JCB]

The concentration at 2C can be converted to 25C based on the temperature conversion prediction sheet .

Problems in this experiment included no formation of precipitate at room temperature (25C). Therefore, the solution can not be labeled as saturated or not. Next time, the temperature of the ice bath needs to be taken periodically in order to monitor the temperature decrease. The temperature of the ice bath may not have reached equilibrium.

Conclusion

The objective of this experiment was to determine the solubility of cinnamic acid in methanol at 25C. The solubility was found at 2C due to no precipitation visible at 25C. Next time, more cinnamic acid will be added in hopes of precipitate formation at 25C.

Log

2011-11-22

10:06- hot plate was plugged in and set to 100C. The original temperature of the water was 24C.
10:10- the test tube of cinnamic acid was filled with methanol to the 3/4th mark (on the test tube)
10:12- the test tube was inverted a few times, parafilm was added around the cap and placed in the bath, which was at 30C
10:14- picture #1 was taken (test tube in hot water bath)
10:15- the hot water bath temperature was 32C. the test tube was inverted
10:16- the test tube was replaced in the hot water bath
10:19- the hot water bath temperature was 34C. The test tube was sonicated for about 5 seconds.
10:21- the test tube was replaced in the hot water bath, which was at 35C
10:22- the room temperature water bath was prepared
10:23- the hot water bath temperature was 35C. The test tube was removed from the hot water bath.
10:24- the test tube was placed into the room temperature bath (25C). No precipitate was visible.
10:28- the test tube was sonicated for about 5 seconds
10:28- the test tube was replaced into the 25C room temperature bath. No visible precipitate was formed
10:35- the densities of an empty 5mL volumetric flask was measured to be 18.5010g and the 5mL volumetric flask filled with methanol was measured at 22.4417g
10:36- the test tube was sonicated for about 5 seconds in hopes of creating precipitate
10:37- the test tube was replaced in the room temperature bath (25C). No precipitate was visible.
10:49- the room temperature bath was 25C. No precipitate was visible.
11:03- the room temperature bath was 25C. No precipitate was visible.
11:03- the temperature of the bath was adjusted with cool water.
11:07- the temperature of the room temperature bath was 25C.
13:05- the temperature of the room temperature bath was 25C. Ice was added.
13:29- the temperature of the bath was 3C.
13:32- the temperature of the bath was 2C. Precipitate was visible. Densities in a 1 mL volumetric flask were taken. The flask was cleaned, dried and weighed. The empty flask was 20.3766g. The methanol was 21.1525g. The solution was 21.2111g.