exp317

=Researcher= Rida Atif

=Objective= To determine the recrystallization yield of benzoic acid in ethanol/water (12:20) to __#|confirm__ results of EXP304

=Procedure= An empty erlenmeyer flask with a cap was massed. About 1g of benzoic acid was added into the flask and massed again. 12mL of ethanol and 20mL of water was added into the flask and massed again. The whole flask was put onto a hot plate until the benzoic acid dissolved into the flask; when the solute dissolved, the flask was removed from the hot plate and set to cool down over the weekend.

=Results= [|Calculation Sheet] The solubility of the solution at boiling point was 0.251M With this solubility and a room temperature solubility of 0.19M, the predicted recrystallization yield was 24.3%; however, the actual yield was 0%.

=Discussion= No crystals formed in the flask while it was left over the weekend. This could be because in this experiment, the ethanol and water were combined before they were used to dissolve the benzoic acid whereas in EXP304 the ethanol was used first then water. This experiment, and its ratios of solute and solvents, was based off [|Lab02] in which 41% of the benzoic acid was recrystallized. The temperature curve predicted a boiling point solubility of 2.21M which means about 91% of the solute is expected to be recrystallized.

=Conclusion= This experiment should be repeated but with the solvents being added into the flask as they were in EXP304, since that actually yielded crystals and with the same solubility

=Log=

2012-07-13
9:29 - Turned on hot plate to 170C 9:35 - Mass of empty 50mL erlenmeyer flask and cap: 49.8289g 9:40 - Mass of flask, cap, and benzoic acid: 50.8352g 9:46 - Measured 9.36g of ethanol and put in separate 50mL flask. (this is equivalent to 12mL of ethanol with a density of 0.76g/mL) 9:54 - Measured 20g of water and put in the flask with the ethanol (this is equivalent to 20mL of water with a density of 1.00g/mL) 9:57 - Added the ethanol/water mixture into the flask with the benzoic acid and set on hot plate 10:17 - All of the benzoic acid has dissolved into the solvent mixture. The flask was removed from the hot plate and set to cool down 10:29 - No crystals have formed inside the flask yet. 10:34 - Mass of flask, cap, crystals, and ethanol/water: 79.903g 10:36 - Covered flask with parafilm to prevent any solvent from evaporating overnight 10:37 - Mass of flask, cap, crystals, ethanol/water, and parafilm: 80.619g

2012-07-16
9:26 - No crystals formed in the flask over the weekend