Question

Arrange the following in order of increasing acidity Methane, carboxylic acid, phenol and alcohol

Answer 1

Acidity strength is determined by the ability of compound to donate H⁺ 
The easier it lose H⁺ the stronger will be the acid 
also the more stable conjugate base formed the stronger will be the acid
So the arrangement will be:
Methane < Alcohol < Phenol < Carboxylic acid
because carboxylic anion (COO-) is more stable than phenoxide (Ph-O⁻) than alkoxide RO⁻ than CH₃⁻