Naphthalene, a non-polar aromatic hydrocarbon with molecular formula C10H8, is often used to demonstrate differences in solvent polarity. Consider the solubility of naphthalene at 25 °C in each of the following solvents:
• Toluene (C7H8) – a non-polar aromatic liquid
• Ethanol (C2H5OH) – a moderately polar protic liquid
• Water (H2O) – a highly polar protic liquid
Answer the questions that follow.
(a) Predict which of the three solvents will dissolve the greatest mass of naphthalene per unit volume. Justify your prediction briefly.
(b) Between ethanol and water, identify which will dissolve more naphthalene and explain your reasoning in terms of specific intermolecular forces present in each solvent.
(c) Suppose an equal mass of naphthalene is placed in each solvent and the mixtures are stirred until equilibrium is reached. Describe the macroscopic appearance you would expect for each mixture (e.g., clear solution, suspension, remaining solid) and relate your observations to molecular interactions.