Question

10 multiple answer 1 point why is methanol cooled before rinsing the crystals during vacuum filtration? cooling methanol removes volatile impurities. hot methanol helps crystals adhere to the funnel. cold methanol prevents dissolution of the purified naphthalene. cold methanol dissolves remaining impurities more effectively.

Explanation:

• Option 1: Cooling methanol does not remove volatile impurities; this is incorrect.
• Option 2: Hot methanol's effect on crystal adhesion to the funnel is not the reason for cooling; incorrect.
• Option 3: Naphthalene's solubility in methanol decreases with lower temperature. Cold methanol prevents the purified naphthalene from dissolving, which is crucial to retain the crystals. Correct.
• Option 4: Impurities often have different solubility properties, and cold methanol can dissolve remaining impurities (since impurities might be more soluble in cold methanol or the desired compound less so, allowing impurity removal without losing product). Correct.

Answer:

C. Cold methanol prevents dissolution of the purified naphthalene, D. Cold methanol dissolves remaining impurities more effectively