Arrange the following in increasing order of their pK, values.

(A) o-nitrophenol
(B) m-nitrophenol
(C) Phenol
(D) Ethanol

Choose the correct answer from the options given below:

(A), (B), (C), (D)

The correct answer is Option (1) → (A), (B), (C), (D)

pKₐ increases as acidity decreases.

Relative acidity of the given compounds:

• o-Nitrophenol → strongest acid (−I and −R effects of NO₂)
• m-Nitrophenol → slightly less acidic (−I effect only)
• Phenol → weaker acid
• Ethanol → weakest acid

So, increasing order of pKₐ values is:

$\text{o-Nitrophenol (A)} < \text{m-Nitrophenol (B)} < \text{Phenol (C)} < \text{Ethanol (D)}$