Question

4 multiple answer 1 point which property of a good recrystallization solvent is most essential? ability to dissolve impurities at all temperatures high solubility of the compound at high temperature high solubility of the compound at low temperature low boiling point to evaporate easily

Explanation:

To determine the most essential property of a good recrystallization solvent, we analyze each option:

• Option 1 (Ability to dissolve impurities at all temperatures): While dissolving impurities is useful, it's not the most essential. The main goal is to purify the target compound, so this is secondary.
• Option 2 (High solubility of the compound at high temperature): This is crucial. In recrystallization, we dissolve the impure compound in a hot solvent (so high temp solubility is needed to get a saturated solution). Then, on cooling, the compound crystallizes out (since its solubility at low temp is low), leaving impurities dissolved or undissolved. Without high solubility at high temp, we can't get enough of the compound into solution to recrystallize it effectively.
• Option 3 (High solubility of the compound at low temperature): If the compound is highly soluble at low temp, it won't crystallize out when the solution cools, which defeats the purpose of recrystallization. So this is undesirable.
• Option 4 (Low boiling point to evaporate easily): A low boiling point is convenient for removing the solvent after recrystallization, but it's not the most essential property. The core process of recrystallization (dissolving and then crystallizing the target compound) relies on the solubility behavior with temperature, especially high solubility at high temp.

Answer:

B. High solubility of the compound at high temperature, D. Low boiling point to evaporate easily, A. Ability to dissolve impurities at all temperatures (Note: Actually, the most essential is high solubility at high temp, but sometimes multiple answers are correct. Let's re - evaluate:

• A: Dissolving impurities at all temps is good (so impurities stay dissolved or undissolved while compound crystallizes), so it's a desired property.
• B: High solubility at high temp is essential to get the compound into solution.
• D: Low boiling point is good for removing solvent after.
• C is bad as explained. So the correct options are A, B, D. But the question says "MOST essential". If we have to pick the most essential, it's B. But as a multiple - answer, let's check standard recrystallization solvent properties:

1. The solvent should dissolve the solute (compound) well at high temperatures.
2. The solvent should dissolve the solute poorly at low temperatures (so C is wrong).
3. The solvent should dissolve impurities either very well (so they stay in solution when cooled - option A) or very poorly (so they can be filtered out before heating).
4. The solvent should have a reasonably low boiling point (option D) so it can be removed easily from the crystals.

So the correct options are A, B, D. But if the question is about the MOST essential, B is the key for the recrystallization process (dissolving the compound to purify it), but A and D are also important properties. However, in many recrystallization discussions, the high solubility at high temp (B) is the core for the process to work, while A and D are also desired. So the answer depends on the context, but the standard essential properties include A, B, D.