Exp176

=Researcher= Sozit Kurtu =Objective= To determine the solubility of cinnamic acid in methanol using density measurement. Volumetric flask size effect on percent error was also examined. The additivity of volumes is an [|assumption] and the density of the solid is obtained from ChemSpider prediction. =Procedure= =Results= [|Calculations] [|Measurements]
 * Flask (after evap) || Concentration (M) ||
 * 1C - 1mL || 1.390 ||
 * 3C - 5mL || 1.270 ||
 * 4C - 10mL || 1.280 ||

[Nice photo documentation -AL] =Discussion= It can be assumed that all C samples were from a saturated solution because solid was present in the beaker due to some evaporation. These values agreed with [|literature values], as well as [|previous experimental values] recorded. Because the 20-mL sample was not saturated after the 30min bath at 40C, it should be investigated as to whether this was a matter of time, or another matter. The measured values for density of methanol were different in each volumetric flask, with a standard deviation of 0.0049 between flask sizes. There is no observable trend within the four values. This suggests an error in each flask itself, and should be further investigated as well. =Conclusion= The solubility of cinnamic acid in methanol is represented in the above [|Measurements], with the total weighted mean found to be 1.33M. at approximately room temperature. This is in agreement with [|literature] and [|previous experimental values|other experimental values]. Further, experiment 178 suggests that the higher values are correct under experimental conditions. Experiment 178 also partially addresses the matter of accuracy and precision of volumetric flasks, along with experiment 179. =Log=

2010-09-20
10:28 - Set bath to 40C. Actual temp 22C. 10:38 - Measured ~3.4 g cinnamic acid (excess) into 20mL screw-cap test tube. Bath reached 40C. 10:47 - Set up ring stand for bath. See EXP176pic1. 10:51 - Actual temp 44C. Reset to 40C. 10:53 - Tube not entirely submerged; however, sufficient for saturation process. See EXP176pic2. 10:58 - Temp @ 43C. 11:10 - Set up 25C water bath. 11:15 - Removed tube 1 from 40C bath. Actual temp still 43C. 11:19 - Removed supernatant w/ pasteur pipet. Crystallization occurred on pipet tip and on rim of tube 2. Put in 25C bath. Left lab. 12:55 - Returned. Bath at 22C; no precipitate. 13:01 - Sonicate for ~30 sec. Still no precipitate. 13:05 - Measured dry flask weight (mg). Reason for discrepant intervals between weights is style of flask (See Measurements). 13:09 - Measured flask with methanol (mg). 13:20 - Measured flask with solution (mg). 13:33 - Decanted "waste" solution in beaker because of visible evaporation. Used it to retake the density. See 1C, 2C, 3C, and 4C in Measurements. 13:45 - Took picture of solid remaining from original 20-mL screw-cap test tube (after attempted dissolution for saturated solution). See EXP176pic3.