If a particular solvent dissolves both the compound being purified and impurities at room temperature, is this a good solvent for recrytallization of the compound? Explain your answer.
Read all of the article but pay particular attention to the last paragraph.
http://en.wikipedia.org/wiki/Recrystallization
When considering a solvent for recrystallization, it's generally desirable to choose a solvent that will selectively dissolve the compound being purified while leaving impurities behind. If a particular solvent dissolves both the compound and impurities at room temperature, it might not be an ideal solvent for recrystallization.
To determine the suitability of a solvent, one can conduct a solubility test. Here's how you can perform it:
1. Start by selecting a small sample of the compound to be purified and some known impurities.
2. Take a series of test tubes and add a small amount of the selected solvent to each tube.
3. Gradually heat the tubes, allowing the solvent to dissolve more solute.
4. Continue adding solute until no more dissolves, and you observe a small amount of undissolved solid at the bottom of the tube. This indicates the saturation point of the solvent.
5. If the desired compound dissolves completely at high temperatures but recrystallizes upon cooling, it suggests that the solvent is suitable for recrystallization.
However, if both the compound and the impurities dissolve at room temperature, it may indicate that the solvent is not selective enough for recrystallization. In such cases, you might need to consider alternative solvents that exhibit better selectivity.
Keep in mind that the ideal solvent for recrystallization should have a high solubility for the compound at high temperatures, but a low solubility at room temperature. This way, impurities will remain dissolved while the desired compound crystallizes upon cooling, effectively separating the two.