Out of o-nitrophenol and o-cresol which is more acidic ?

Explanation

(1) In o-nitrophenol, nitro group `(NO_(2))` is an electron withdrawing group present at ortho position which enhances the acidic strength (`-I` effect). The `O-H` bond is under strain and release of proton`(H^(+))` becomes easily. Further o-nitrophenoxide ion is more stabilised due to resonance.
(2) The methyl group in o-creasol is an electron releasing group which decreases the acidic strength (`+I` effect). The electron density on the ring as well as on the `O-H` bond increases. This makes the release of `H^(+)` ion difficult. In other words, o-cresols have less tendency to form stable phenoxide ion by releasing a proton.

Hence, o-nitrophenol is more acidic than o-cresol.