Acidic nature of monocarboxylic acids

(1) Cause of acidic nature

(a) A atom of carboxylic acid may be illustrated as a resonance hybrid of the following structures.

(b) because of electron deficiency on oxygen atom of the hydroxyl group, there is a distance of electron pair of O-H bond in the direction of the oxygen molecule. These make easy the release of hydrogen as proton (H⁺).   

(c) The resultant carboxylate ion also stabilized by resonance (like negative charge is dispersed on both of the oxygen atom). It raises the stability of carboxylate anion and makes it weaker base or strong acid.