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Solubility book (3rd Edn)
Lizzie Clark with Lacey Condron and Andrew Lang
To measure the solubility of palmitic acid in 1-propanol using the density method.
25 mL volumetric flask
Hot Water Bath
Chemical Spatula (for measuring out solute)
1. Put on safety gear including goggles, lab coat, and gloves.
2. Gather the materials listed above.
3. Measure and record the temperature of the balance room (preferably in Celcius to make later calculations easier).
4. Using the electron balance, weigh and record the empty 25 mL volumetric flask (g).
5. Carefully pour 25 mL of 1-propanol into the volumetric flask.
6. Using the electronic balance, measure and record the weight of the filled volumetric flask and propyl acetate.
7. Calculate the predicted amount of trans-cinnamic acid needed for saturation of 30mL of 1-propanol, plus 33% more than that. Measure out this amount of trans-cinnamic acid using the electron balance. Record weight.
8. Pour approximately 30mL of 1-propanol into a 100mL beaker.
9. Add measured amount of palmitic acid to the propyl acetate in the beaker, swirl, and parafilm.
10. Measure and record the temperature of the laboratory area (in Celsius).
11. Place beaker in warm water bath of around 45C and observe until crystals form (indicating that the solution is saturated).
12. Weigh empty 25mL volumetric flask (to assure that it is the original one used or to obtain the new weight).
13. Pipette 25mL of the saturated 1-propanol + palmitic acid solution into flask and weigh.
The solubility of palmitic acid in 1-propanol at 25 C was measured to be 0.89 M.
See Calculation Spreadsheet
9:35- Room temperature at 20.0 C. Empty 25mL volumetric flask weighed 20.0405g.
9:39- Volumetric flask with the 25mL of 1-propanol weighed 40.1094g.
9:44- Tarred balance with weigh paper and measure out 6.3419g of palmitic acid. (This was a rough mid point between the drastically different predicted values of needed palmitic acid for 1-propanol and 2-propanol.)
9:48- Added palmitic acid to 30mL of 1-propanol in a 100mL beaker and parafilmed.
9:52- Warm water bath temperature measured at 48.0 C.
9:54- Placed beaker in warm water bath and swirled until dissolved, adding warm water as needed to sustain the temperature.
10:02- Solute completely dissolved. Beaker removed and placed in a 23.0 C water bath to cool.
10:14- Cool water bath measured now at 25.0 C.
10:45 Weight of empty 25 mL volumetric flask at 18C was 20.0687g
11:00 Could not extract the full 25mL of supernatant from beaker, the volumetric flask was filled to just below the neck. The beaker contained a slush. Aprroximately 15mL of 1-propanol was added to the beaker with slush.
11:05 The beaker was parafilmed and placed in a water bath at 48C
11:15 All crystals had re-dissolved and the beaker was placed in a 25C water bath.
11:55 Crytals had formed in the bottom of the beaker and approximately 3mL of supernatant (25C) was added to the volumetric flask to bring the contents up to 25mL. Some crystals had formed at the bottom of the volumetric flask.
12:00 The weight of the flask plus contents was 40.4750g.
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