Solubility Tests and Recrystallization Lab Write Up
Five compounds were added to four different solvents. The solvents were all clear liquids. The compounds were Anthracene, a thin white powder, Benzoic Acid, a crystalline white solid substance, Phthalic Acid, a white solid substance, Resorcinol, solid, white â€œpebblesâ€ and Sodium Aphthionate, a fine pinkish coloured â€œsandâ€ like material. Table 1 describes how soluble each compound was in the different solutes. Approximately 100 mg of each compound was added to approximately 3 mL of solvent. Many solutes showed no solubility within a given solvent and the two substances would remain in distinctly different ...view middle of the document...
96 grams |
Container | 11.90 grams |
Recrystalized Salicylic Acid in Container | 12.52 grams |
Alizran Yellow (2%) | 0.0192 grams |
Charcoal | 0.02 grams |
Original sample of Salicylic Acid: 0.96 grams (-2% Alizran Yellow = 0.0192 grams) = 0.9408 grams
Cup weight: 11.90 grams
Recovery sample in cup: 12.52 grams
Recovery sample weight: (12.53 â€“ 11.90 grams=) 0.629 grams
0.629/.9408 grams = 0.6562
= 65.62% yield.
Table 3: IR Values for Salicylic Acid
Bonds | Experimental Value | Literature Value |
(C=O) | 1667.53 cm-1 | 1730-1750 cm-1 |
(C=C) | 1613.16 cm-1 | 1680-1640 cm-1 |
(O-H) | 3238.77 cm-1 | 3400-2500 cm-1 |
There was a 65.62% product yield with the Salicylic Acid in the experiment. The crystals observed in the solubility experiment ranged from amorphous (Benzoic Acid in Toluene, Ethanol and Water), prism (Phthalic Acid in Ethanol and Sodium Napthionate in Water) or needle shaped (Resorcinol in Ethanol). The Salicylic Acid also displayed a needle shape when it crystalized. The crystals were all clear in colour. Within the IR stretch values observed, Carboxylic Acid, (O-H) and (C=O), were observed at 3238.77 cm-1 and 1667.53 cm-1 respectively. The Aromatic (C=C) was observed at 1613.16 cm-1.
The C=O bond is around 30 cm-1 lower than literature values because of the conjugated C=C bond, which shifts the value down. The only experimental value that falls within the ranges given is the O-H bond, suggesting this compound is not entirely pure. This is understandable given the compound was transferred between a different containers and may have picked up trace amounts of chemicals from other containers, despite best attempts to keep them clean.
The solvents and solutes all represented different levels of polarity and therefore, have different structures. The solvents (in order of increasing polarity) were: Ligroin, Toluene, Ethanol and Water. The notion of choosing â€œalikeâ€ solvents and solutes is too encourage solubility within the solvent. Solvents may be too powerful, though, which may increase the difficulty of removing the desired material from the solution. Sometimes when a solvent is too powerful, a slightly less powerful one will dissolve better when heated. The power of a solvent increases within its own functional group, dependent on how high the boiling point of each solvent is. As long as the solvent does not react with the compound and is not heated past its own melting point (so the solid compound does not melt) this should help the experimenter choose a solvent for their solute. Charcoal was also an important reagent used in this experiment, as it was able to absorb coloured impurities and allow them to be filtered out of the solution which resulted in clear, salicylic acid crystals. In the experiment discussed here, the charcoal was highly effective and when the solution was filtered by gravity (after the charcoal was added) resulted in a clear coloured...