(a) Why is phenol more acidic than cyclohexanol?

• Step 1 (Governing Principle): [0.5 Mark] The acidity of a compound depends on the stability of its conjugate base (phenoxide ion vs. cyclohexoxide ion). In phenol, the lone pair of electrons on the oxygen atom is in conjugation with the $\pi$-electrons of the benzene ring.
• Step 2 (Step-by-Step Reasoning): [0.5 Mark] The phenoxide ion formed after the loss of a proton ($H^+$) is stabilized by resonance. The negative charge is delocalized over the ortho and para positions of the benzene ring. In contrast, the cyclohexoxide ion (from cyclohexanol) lacks resonance stabilization, as the cyclohexane ring is saturated and cannot delocalize the negative charge.
• Step 3 (Final Concluded Answer): [0.0 Mark] Due to the resonance stabilization of the phenoxide ion, the equilibrium for the dissociation of phenol lies further to the right compared to cyclohexanol, making phenol a stronger acid.

(b) Give one chemical test to distinguish between the two.

• Step 1 (Chemical Reaction): [0.5 Mark] Neutral Ferric Chloride ($FeCl_3$) Test: Phenol reacts with neutral $FeCl_3$ to form a violet-colored complex, whereas cyclohexanol does not show this reaction.
• Step 2 (Reaction Equation): [0.5 Mark] $$6C_6H_5OH + FeCl_3 \rightarrow [Fe(OC_6H_5)_6]^{3-} + 3H^+ + 3HCl$$
  (Or simply: $C_6H_5OH + FeCl_3 \rightarrow \text{Violet complex}$)