1. Successful purification by recrystallization is based primarily on the solubi
ID: 872924 • Letter: 1
Question
1. Successful purification by recrystallization is based primarily on the solubility of a solute in a solvent. With the water solubility values given, which one or more of these solutes would recrystallize effectively in water? If not, identify the specific experimental issue you would encounter when recrystallizing.
2. Suggest 3 reasons why we employ water instead of ethanol as the recrystallization solvent for the unknowns?
H2N OH OH 0.3 g/100 mL 20 °C 24.99 g/100 mL 25 °C 0.2 g/100 mL 20 °C 0.1 g/100 mL 22 °C 0.0009 g/100 mL 25 °CExplanation / Answer
The solids that would recrystallize effectively in water are those of solubility
0.3 g/100 ml
0.2 g/100 ml
0.1 g/100 ml.
not effective:
0.0009g/100ml because the solubility is too low and it is expected to not increase much with the temperature
24.99g/100 ml because the solubility is too much high and it is expected to not change much with the temperature, so there will be much loss of solid by solubility.
2) - it is cheaper
- The difference between the room temperature and boiling point is larger than ethanol (75 oC vs 53 respectively) allowing more solute to dissolve.
- With water there is less losses by evaporation when heating.
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