Write a note on hydrogen halides. Explain the reactivity of halogens with oxygen. $OR$ Write a note on oxides of halogens.

(N/A) All halogens react with hydrogen to form hydrogen halides $(HX)$,but the affinity for hydrogen decreases from fluorine to iodine. Hydrogen halides dissolve in water to form hydrohalic acids. The acidic strength increases in the order: $HF < HCl < HBr < HI$,while thermal stability decreases in the order: $HF > HCl > HBr > HI$. Except for $HF$,which is liquid due to intermolecular hydrogen bonding,all hydrogen halides are gases.
Halogens form many oxides with oxygen,but most are unstable. Fluorine does not form oxides; its compounds with oxygen are called fluorides (e.g.,$OF_2$,$O_2F_2$) because fluorine is more electronegative than oxygen. Chlorine forms $Cl_2O$,$ClO_2$,$Cl_2O_6$,and $Cl_2O_7$,which are strong oxidizing agents. $ClO_2$ is used for bleaching and water treatment. Bromine oxides ($Br_2O$,$BrO_2$,$BrO_3$) are the least stable and exist only at low temperatures. Iodine oxides ($I_2O_4$,$I_2O_5$,$I_2O_7$) are insoluble solids; $I_2O_5$ is a powerful oxidizing agent used for the estimation of carbon monoxide. The stability order of halogen oxides is $I > Cl > Br$.