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Solubility book (3rd Edn)
To measure the solubility of palmitic acid in methanol 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 methanol into the volumetric flask.
6. Using the electronic balance, measure and record the weight of the filled volumetric flask and methanol.
7. Calculate the predicted amount of palmitic acid needed for saturation of 30mL of methanol, plus 10% more than that. Measure out this amount of palmitic acid using the electron balance. Record weight.
8. Pour approximately 30mL of methanol into a 100mL beaker.
9. Add measured amount of palmitic acid to the methanol 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 methanol + palmitic acid solution into flask and weigh.
The solubility of palmitic acid in methanol at 25 C was measured to be 0.27 M. See
9:22- Empty 25 mL volumetric flask weighed 20.052g.
9:27- Volumetric flask with 25 mL weighed 39.949g.
*Room temperature at 19.5 C
9:29- Predicted amount of solute + 10% is 3.84g of palmitic acid. Measured out 3.845g of palmitic acid.
9:33- Added palmitic acid amount to 30mL of methanol in 100 mL beaker.
9:34- Parafilmed and placed in 48 C warm water bath and swirled till all solute dissolved.
9:38- All solute dissolved. Placed beaker (still parafilmed) in 28 C water bath, which was cooling to 25 C.
9:57- Solution turned to slush. Added 20 mL of solvent (methanol) to the beaker and redissolved in 46 C water bath.
10:05- All solute dissolved. Placed beaker in 26 C water bath to cool.
10:33- Empty flask weighed 20.051g.
10:38- filtered solutions to obtain 25 mL of liquid.
10:40- Supernatant in beaker weighed 40.064g.
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