EXP238

Researcher
Stephanie Costa

=Objective= To determine the solubility of [|cinnamic acid] in chloroform. The additive volumes is [|assumptive].

=Procedure= Cinnamic acid was dissolved in chloroform in a 42-47 C hot water bath for ten minutes. The solution was cooled to room temperature for 20 mminutes. The supernatant was moved to a room temp 5mL volumetric flask, and then measured in a 1mL volumetric flask in order to determine the solubility of cinnamic acid. The density method was used.

=Results= [|Density sheet 1]
 * [Not all measurements are recorded here JCB]**

[|Calculations sheet]

Solubility varying with time is shown by this [|graph]
 * [The key result is missing - how does the concentration vary with time in the heating bath? You can do a quick plot. JCB]**

Precipitate was visible throughout the experiment. The supernatant was removed from the samples by filtering it. The molar concentration of the sample after 49 minutes was 1.1476M and the molar concentration of the samples after 2 hours 10 minutes was found to be 1.2904M at 25C. **[is this what you mean? JCB]**

=Discussion= Precipitate was seen throughout this experiment. The density was taken many times throughout this experiment, however, the final measurements were accurately taken at the same time. At 25C, the concentration was 1.2904 M. Therefore, the solubility of cinnamic acid in chloroform at 25C is 1.2904 M.

The resulting solubility found in this experiment was concurrent with some of the solubilities calculated from other [|experiments]. The solubility of cinnamic acid found at 25C by this experiment is higher than the average, which is 0.9661 M, and does not compare favorably to the [|Seidell book] calculated solubility which was 0.8166. **[Turns out it doesn't agree with Seidell - check again JCB]**

There were some problems in this experiment. The solution was not cooled before taking the supernatant. The supernatant, once removed, then cooled at room temperature. The empty flask was not weighed the first time the densities were measured, so the measurement in the 5mL volumetric flask were unable to be used; therefore, those measurements do not appear in the data sheet because they were incomplete.

Time dependence data makes sense (see data sheet with measurements taken at two different times). As the time progressed, the concentration of the samples increased also. This could relate to the equilibrium of the samples. The samples may not have reached equilibrium when the first measurement was taken, therefore the concentration (solubility) would increase as the samples reached equilibrium. =Conclusion=
 * [Does the time dependence data make sense? JCB]**

The objective of this experiment was to determine the solubility of cinnamic acid in chloroform. The solubility of cinnamic acid in chloroform after 49 minutes was 1.1476M and after 2 hours and 10 minutes was 1.2904M at 25C. **[Is that unambiguous? JCB]**

=Log=

2011-11-22
10:51- the hot water bath was set to 140C. 10:54- 4.0234g of cinnamic acid was weighed out 10:58- chloroform was added to the 3/4th mark on the 20mL screw caop test tube. 11:01- parafilm was added around the cap and the test tube was placed into the hot water bath, which was at 42C 11:04- the hot water bath temperature was 44C. The test tube was inverted. 11:08- the hot water bath temperature was 46C. The test tube was inverted. 11:10- the hot water bath temperature was 47C. The test tube was inverted. 11:11- the hot water bath was turned off. 11:15- the weight was taken. In a 5mL volumetric flask, chloroform was 25.8834g. 11:22- the water bath was 45C. The solution was pipetted out for density calculation. In a 5mL volumetric flask, the mass of the solution was 25.6267g. Then was left to sit in room temperature. **[Assign a label to each sample so you can refer to them in the spreadsheet JCB]** 11:42- the weight of chloroform was taken in a 1mL volumetric flask. It was measured at 21.4196g 11:50- the measurements up until this point were discarded due to procedural error. DENSITY 1B: the density of the supernatant of the solution was taken in a 1mL volumetric flask. It was measured at 21.8007g. The mass of the empty 1mL volumetric flask was measured to be 20.3800g. The mass of chloroform was measured again in a 1 mL volumetric flask to found to be 21.8281g. **[Was there new solid at this point and did you take the supernatant? JCB]** 13:11- DENSITY 2B: the density of the supernatant after sitting in room temperature (25C) was taken. In a 1mL volumetric flask, the empty 1mL volumetric flask was 20.3766g. The solution was 21.8071g. The chloroform was 21.8403g.