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

Explanation

Due to -I and -R-effect of the `NO_(2)` group, electron density in the O-H bond decreases while due to +I or hyperconjugation effect, of the `CH_(3)` group, the electron density in the O-H bond increases.

As a result, O-H bond is o-nitrophenol is much weaker than the O-H bond is o-cresol and hence o-nitrophenol is much more acidic than o-cresol.