Identify the characteristics of a good recrystallization solvent. Select one or more: Dissolves a chemical sample well at high temperatures. Is not an organic liquid with a low boiling point. Does not dissolve a chemical sample well at high temperatures. Identify the characteristics of a good recrystallization solvent. Select one or more: Dissolves a chemical Does not dissolve a chemical sample well at low temperatures.
The Correct Answer and Explanation is :
The correct characteristics of a good recrystallization solvent are:
- Dissolves a chemical sample well at high temperatures.
- Does not dissolve a chemical sample well at low temperatures.
Explanation:
Recrystallization is a method used to purify a solid compound by dissolving it in a solvent at an elevated temperature and then allowing the purified solid to crystallize out as the solution cools. To achieve a successful recrystallization, the solvent must meet several key criteria:
- Dissolves a chemical sample well at high temperatures: A good recrystallization solvent should be able to dissolve the compound of interest when heated to a high temperature. The high temperature increases the solubility of many compounds, allowing them to be completely dissolved in the solvent. This step ensures that the impurity remains in the solution and does not crystallize with the desired compound.
- Does not dissolve the chemical sample well at low temperatures: After the sample is dissolved in the hot solvent, the solution is cooled to room temperature or below. A good solvent for recrystallization should have a decreased solubility for the compound of interest at lower temperatures. This allows the dissolved compound to crystallize out of the solution, leaving behind any impurities that remain in the solvent.
Other important characteristics of a good recrystallization solvent include:
- Selective solubility: The solvent should dissolve the compound of interest at high temperatures but not the impurities, or it should have a significantly lower solubility for impurities.
- Boiling point: A good solvent should have a boiling point that is not too high, so it can be easily evaporated once recrystallization is complete. However, it should not be a low boiling point liquid as it may evaporate too quickly, especially when heating the solution.
- Non-toxicity and safety: The solvent should be relatively safe to handle, with low toxicity and flammability risks.
By meeting these criteria, recrystallization can successfully purify the chemical sample, removing contaminants and obtaining high-purity crystals.