"What will be the correct increasing order pf acidic strength of : HF, HCl, HBr, HI"

HF < HCl < HBr < HI

The correct answer is 2. HF < HCl < HBr < HI.

The acidity of a hydrogen halide (HX) increases as the size of the halogen atom increases. This is because the larger the halogen atom, the weaker the bond between the hydrogen atom and the halogen atom. This makes it easier for the hydrogen atom to dissociate from the molecule, which is what happens when an acid reacts with a base.

So, HF is the weakest acid and HI is the strongest acid of the hydrogen halides.

Here is a table showing the increasing order of acidic strength of the hydrogen halides: