Among the following four compounds (i) Phenol (ii) Methyl phenol (iii) Meta-nitrophenol (iv) Para-nitrophenol The acidity order is:

In phenols, the presence of electron releasing groups decreases the acidity, whereas presence of electron withdrawing groups increase the acidity, compared to phenol. Among the meta and para-nitrophenols, the latter is more acidic as the presence of -NO2 group at para position stabilizes the phenoxide ion to a greater extent than when it is present at meta position. Thus, correct order of acidity is : Para-nitrophenol(iv) > meta-nitrophenol(iii) > phenol(i) > methylphenol(ii)