Researcher

Evan Curtin

Objective

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

Results

Google Spreadsheet - Exp197-1
The molarity of a solution of methanol saturated with cinnamic acid was found to be:
For the 5mL volumetric flask: 1.337 M
For the 2mL volumetric flask: 1.348 M
For the 1mL volumetric flask: 1.492 M

Discussion

Previously measured solubility of cinnamic acid in methanol had a range of 1.3-1.52 M. The range in this experiment was 1.337-1.492 M. The 1mL volumetric flask had a calculated molarity of 1.492M, which is higher than is expected from experiment 178 (marked as DONOTUSE). The average solubility in the database is currently 1.43M, consistent with the 1.337M and 1.348M determined in this experiment.

Conclusion

The density method was successfully performed.

Log

2011-01-14
14:20 - Set water bath temperature to 40C
15:27 – Put 5.9g of cinnamic acid into a 20mL tube with screw cap and added methanol to fill most of the tube while leaving space. Shake the mixture by hand and with a vortex
15:32 – Placed the tube with cinnamic acid and methanol into the water bath, temperature now at 40C.
15:45 – Placed empty 10mL flask onto scale and re-zeroed. Add 10mL of pure methanol and measured. Repeated for 1mL, 2mL and 5mL flasks. Emptied the flasks. Placed flasks in oven to dry.
16:36 – Temperature of water bath is 40.5C. Removed tube containing cinnamic acid solution from the bath. Decanted the supernatant immediately. Within seconds, crystals precipitated from the solution. Set on table to cool.
16:40 – Set temperature of bath to 25C
17:04 – Temperature of bath is 25C. Place saturated solution of cinnamic acid in bath.
17:45 – Removed solution from bath, immediately separated the supernatant from the precipitate. Small crystals would scatter the light, but the solution in this case was clear. Weighed the concentrated solution in volumetric flasks of volumes 5mL, 2mL and 1mL. Not enough supernatant to weigh the 10mL. [AL: Excellent log so far]