The correct sequence or order of acidic strength of HF, HCl, HBr, and HI is:
HI> HBr> HCl> HF
HBr> HI> HCl> HF
HF> HCl> HBr> HI
HCl> HF> HBr> HI
The acidic strength of HF, HCl, HBr, and HI varies in order :HI> HBr> HCl> HF.It increases down the group.Acidic strength depends on the bond strength between hydrogen and halides as the size increases going down the group liberation of H+ ions becomes easier due to increased size and weak bond strength.