Following are a group of compounds showing acidic behaviour: Phenols are less acidic than carboxylic acids. Why?

Answer

This is because phenoxide `(C_6H_5O^(theta))` ion is less resonance stabilised than carboxylate anion `R-COO^(theta)`. In three resonance structures of phenoxide ion, the negative charge is on less electronegative carbon. But in carboxylate ion, negative charge is one more electronegative oxygen.