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


F2 can oxidize Cl- to Cl2, Br- to Br2, and l- to l2 as:
F2aq+2C-ls2F-aq+ClgF2aq+2Br-aq2F-aq+Br2lF2aq+2l-aq2F-aq+l2g
On the other hand, Cl2, Br2, and l2 cannot oxidize F- to F2.

The oxidizing power of halogens increases in the order of 

l2<Br2<Cl2<F2.

Hence, fluorine is the best oxidant among halogens.

Hl and HBr can reduce H2SO4 to SO2, but HCl  and HF cannot

Therefore, Hl and HBr are stronger reductants than HCl and HF

2Hl+H2SO4l2SO2+2H2O2HBr+H2SO4Br2+SO2+2H2O

Again, l-can reduce Cu2+ to Cu+, but Br- cannot.

4l-aq+2Cu2+aqCu2l2g+l2aq

Hence, hydroioic acid is the best reductant among hydrohalic compounds.

Thus, reducing the power of hydrohalic acid increases in the order of HF<HCl<HBr<Hl.