Phenols do not exhibit the same pKa values as other alcohols; they are generally more acidic. Using the knowledge that hydrogen acidity is directly related to the stability of the anion for (conjugate base), explain why phenol is much more acidic than cyclohexanol.

Acidity is a measure of ionization. An acid will dissociate to proton (H+) and the conjugate base (or anion). The more stable the anion is, the stronger the acid. In your example, phenol dissociates to phenoxide anion. This anion is resonance stabilized -ie- the negative charge is spread out from the oxygen to 3 of the ring carbons. In cyclohexanol anion, the charge is not resonance stabilized and the minus charge is firmly placed on the one oxygen atom.