A strip of cellulose paper was spotted with an equimolar mixture containing phenol (C6H5OH), acetone (CH3COCH3), and methanol (CH3OH). The chromatogram was developed using a 70\% (v/v) acetone–water mobile phase and allowed to dry. The following Rf values were measured:
• Spot X: Rf = 0.78
• Spot Y: Rf = 0.52
• Spot Z: Rf = 0.21
Assume all three compounds remain chemically intact during the experiment.
(a) Identify which spot (X, Y, or Z) corresponds to each compound. Provide a clear justification that references molecular structure and specific intermolecular forces.
(b) Describe how decreasing the percentage of acetone in the mobile phase to 50\% (v/v) would affect the Rf of each compound. Explain your reasoning in terms of the strength of interactions with the stationary and mobile phases.
(c) Predict whether replacing the cellulose paper with a silica gel plate would increase, decrease, or leave unchanged the separation between phenol and methanol under the original 70\% acetone conditions. Support your prediction with an explanation based on the structural features of silica gel.