Ethylene glycol, HO-CH₂-CH₂-OH, is added in equal mass portions to two separate solvents—water and liquid hexane (C₆H₁₄)—both maintained at the same temperature. After vigorous stirring and settling, one test tube shows a single liquid phase; the other shows two distinct layers.
(a) Identify which solvent produces the single-phase mixture. Justify your answer by referring to specific intermolecular forces present between ethylene glycol and each solvent.
(b) Provide a detailed, labeled particulate-level representation for the single-phase mixture. Include at least one ethylene glycol molecule and four solvent molecules, and indicate all hydrogen bonds or other relevant intermolecular attractions.
(c) Predict qualitatively how replacing both –OH groups in ethylene glycol with –OCH₃ groups would affect its solubility in water and in hexane. Explain your reasoning in terms of changes to molecular polarity and intermolecular forces.