Final answer:
The correct order of acids from least acidic to most acidic is Phenol, acetic acid, benzoic acid, and 2, 4, 6 - Trinitrophenol, making option (b) the correct answer.
Step-by-step explanation:
To arrange the given acids in increasing order of their acidity, it is essential to understand how various substituents on the aromatic ring affect the strength of the acids. The stronger the acid, the better it donates a proton (H+), and this ability depends on the stability of the remaining anion after deprotonation. Now, let's look into each of these acids.
- Phenol is the least acidic among the given options because the phenoxide ion is stabilized only by resonance within the aromatic ring without any electron-withdrawing groups.
- Benzoic acid is more acidic than phenol because the carboxyl group resonance allows better stabilization of the carboxylate ion over the phenoxide ion.
- Acetic acid features a methyl group attached to the carbonyl function, which has an electron-donating effect, slightly diminishing its acidity when compared to benzoic acid.
- 2, 4, 6-Trinitrophenol (also known as picric acid) is significantly more acidic due to the strong electron-withdrawing nitro groups on the aromatic ring that stabilize the conjugate base through resonance delocalization.
With the above information, we can order the acids from least acidic to most acidic as follows: Phenol, acetic acid, benzoic acid, 2, 4, 6 - Trinitrophenol. Therefore, the correct option is (b).