Final answer:
2-naphthol is more acidic than ethanol due to its phenolic -OH group that allows for resonance stabilization resulting in a lower pKa value. Ethanol, with a higher pKa value, does not have a phenolic -OH, making it less acidic.
Step-by-step explanation:
When comparing the acidity of 2-naphthol and ethanol, we must look at their respective pKa values and structural features that affect acidity. The acidity of a substance is determined by how easily it donates a proton (H+), and the pKa value provides a numerical value for this propensity. Lower pKa values correspond to stronger acids. 2-Naphthol is more acidic than ethanol. This is due to 2-naphthol containing a phenolic -OH group, which is attached to an aromatic ring, allowing for resonance stabilization when the proton is removed. This resonance stabilization leads to a lower pKa value. Phenol, a similar compound, has a pKa of approximately 10, indicative of this enhanced acidity. On the other hand, ethanol's pKa is around 16, which is higher than phenol's, making it a weaker acid. The presence of the phenolic -OH group makes 2-naphthol more acidic, not ethanol.
Therefore, option 3) '2-naphthol is more acidic because it has a lower pKa value' is the correct answer. It is important to note that despite both 2-naphthol and ethanol having an -OH group, the unique properties of the phenolic -OH group in 2-naphthol is what accounts for its increased acidity. Thus, option 4) 'Ethanol is more acidic because it has a phenolic -OH group' is incorrect, as ethanol does not contain this group.