Justify giving reactions that among halogens, fluorine is the best oxidant and among hydrohalic compounds, hydroiodic acid is the best reductant.

Explanation

(a) `to` The Oxidising capacity of any substance depends on the net result of several contributing energy factors like enthalpy change in a reaction , standard Electrode potential.
`to` With reference to Born- Haber type energy cycle the change in enthalpy value is greater for fluorine.
Greater the magnitude of negative change in enthalpy greater is the Oxidising power.
Supporting reaction :
`to` Fluorine reacts with carbon while the other elements of group do not combine even under drastic conditions.
`C+2F_(2)to CF_(4)`
`to` Fluorine is also called as superhalogen.
(b) `to` Hydrohalic compoundsn acts as reducing agents. Their stability order is
HF.>>HCl > HBr > HI
`to` HI is least stable and acts as strons reducing agent among these halides.
`H_(2)+I_(2)