Researcher

Sozit Kurtu

Objective

To qualify near-melting point behavior with regards to solubility, specifically in the case of cyclohexanecarboxylic acid in hexanes.

Procedure

  1. Make 0.25M, 0.5M, 0.75M, 1.0M, 1.25M, 2.5M, and 5.0M solutions of cyclohexanecarboxylic acid in hexanes at room temperatue.
  2. Set water bath to room temperature to equilibrate.
  3. Insert tubes in a way that facilitates periodic removal to examine samples. Make sure that all samples are completely submerged in the bath.
  4. Decrease temperature in increments of 5C, checking each sample after equilibration for precipitation.
  5. Sonicate periodically to prevent supersaturation.
  6. Continue until sample precipitates, or until the lower limit of water bath.

Results

Calculations
EXP184-1.JPG
EXP184pic1 - Bath apparatus.

EXP184-2.JPG
EXP184pic1 - Bath apparatus, close-up.

Discussion

Hexanes were used rather than pure n-hexane. For accuracy, the experiment should be repeated with n-hexane. Also, due to the melting point of 35-37C, cyclohexanecarboxylic acid exists in a glass-like state at room temperature, which may effect weight measurements. I do not believe that either of these will prove to dispute the following conclusions.

Conclusion

Cyclohexanecarboxylic acid appears to be highly soluble (at least 5M) or totally miscible in hexanes at room temperature and down to -8.5C. Added to SolSum as miscible based on density/MW (8.06M)

Log

2010-10-08


11:30 - Made 0.5M sol'n of cyclohexanecarboxylic acid in hexanes.** (Tube B)
11:42 - Went into sol'n easily.
11:43 - Cleaned flask.
11:45 - Made 0.75M. (Tube C)
11:57 - Required shaking to go into sol'n.
12:00 - Made 0.25M. (Tube A)
12:07 - Made 1M. (Tube D)
12:14 - Went into sol'n, took slightly longer (not quantified).
12:18 - Made 1.25M. (Tube E)
12:27 - Went into sol'n.
12:31 - Set bath to 40C. Actual = 19C. Added samples in 20mL screw-top tubes.
13:18 - Made 2.5M (Tube F). Made 5M (Tube G).
13:34 - Set to 25C. Actual = 40C.
13:45 - Set to 20C. Actual = 25C.
13:53 - Set to 15C. Actual = 20.5C.
14:00 - Sonicated for 20s. Still dissolved.
14:01 - Set to 10C. Actual = 14C.
14:08 - Set to 5C. Actual = 11C.
14:14 - Sonicated for 25s. Still dissolved.
14:16 - Set to 0C. Actual = 4C.
14:23 - Set to -5C. Actual = 1C. Sample G cloudy.
14:32 - Sonicated for 20s. Cloudy sample did not precipitate; heat from sonication caused immediate redissolution.
14:33 - Set to -10C. Actual = -4C. One sample
14:49 - Set to -15C. Actual = ? (misread).
15:05 - Ice formed. -8.5C.