(a) Acids react with base and so does phenol.(b) Upon reaction with active metals such as Na, phenol liberates H2.These two reactions demonstrate the acidic nature of phenol. As compared to ethanol, phenols are more acidic. They lose their H atom as H+ more readily than alcohols.
The reason for such a behaviour of phenol may be attributed to the resonancestabilisation that arises from the contributing structures of corresponding phenoxide ion.The resonance stabilization provided by the contributing structures (I)-(V) more than compensates for the bond breakage energy of O – H bond and thus causes phenol to be acidic in nature.
No such resonance structures are possible for ethoxide ion and therefore the conversion of ethanol to ethoxide is not favoured under normal conditions. Therefore, ethanol is less acidic than phenol.