Question

5 multiple choice 1 point what is the expected solubility behavior of naphthalene in the methanol-water mixture? soluble in both methanol and water at low temperature completely insoluble in both solvents highly soluble in methanol at high temperature but poorly soluble in water at all temperatures insoluble in methanol at high temperature

Explanation:

Naphthalene is a non - polar compound. Methanol is a polar solvent with some non - polar character (due to the methyl group), and water is a highly polar solvent. The solubility of non - polar substances in polar solvents generally increases with temperature (as higher temperature provides more kinetic energy to overcome intermolecular forces). Naphthalene is poorly soluble in water (a highly polar solvent) at all temperatures because of the large difference in polarity. In methanol, at high temperature, the increased kinetic energy helps the non - polar naphthalene molecules to interact with methanol molecules, so it is highly soluble in methanol at high temperature.

• Option 1: Naphthalene is poorly soluble in water even at low temperature, so this is wrong.
• Option 2: Naphthalene is soluble in methanol (especially at high temperature), so this is wrong.
• Option 3: This matches the solubility behavior of naphthalene (non - polar) in methanol (polar with non - polar part, solubility increases with temperature) and water (highly polar, poor solubility at all temps).
• Option 4: Naphthalene is soluble in methanol at high temperature, so this is wrong.

Answer:

C. Highly soluble in methanol at high temperature but poorly soluble in water at all temperatures