Arrange the following compounds in the increasing order of their acid strength: p-cresol, p-nitrophenol, phenol

In p-nitrophenol, the nitro group shows a -M effect (negative mesomeric effect) which stabilizes the conjugate anion; hence, it will be the most acidic. In p-cresol, the methyl group shows a +M effect (positive mesomeric effect) which destabilizes the conjugate anion; hence, it will be the least acidic. Therefore, the acidity order will be: p-cresol < phenol < p-nitrophenol