The ionization constant of phenol is higher than that of ethanol...

The acidic nature of phenol is due to the formation of stable phenoxide ion in solution $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{OH}+\mathrm{H}_{2} \mathrm{O} \rightleftharpoons \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{\text{Phenoxide ion }}^{-}+\mathrm{H}_{3} \mathrm{O}^{+}The phenoxide ion is stable due$ to resonance. \\ The negative charge is delocalized in the benzene ring which is a stabilizing factor in the phenoxide ion and increase acidity of phenol. wheras no resonance is possible in alkoxide ions $\left(\mathrm{RO}^{-}\right)$ derived from alcohol. The negative charge is localized on oxygen atom. Thus, alcohols are not acidic.