Explain the following:
(a) Dry chlorine does not bleach clothes.
(b) Fluorine does not form `F_(3)^(Ө)` (polyhalide) ion.
(c ) `HF` is least volatile and `HCl` is most volatile amongst hydrogen halides.

Explanation

(a) Chlorine acts as a bleaching agent only in the presence of moisture of water, due to liberation of nascent oxygen from water.
`Cl_(2) + H_(2)O rarr 2HCl+[O]`
Hence, dry chlorine cannot bleach clothes.
(b) Fluorine due to absence of d-orbitals in its valence shell cannot expand its coordination number beyond one. Hence `F_(3)^(Ө)` ion is not known.
(c ) In covalent compounds the boiling point increases with increases of molecular mass, as van der waals forces increases. The voltility, thus decreases in covalent compounds with increase in molecular mass. However, hydrogen bonding is present in `HF`. Due to which , the boiling is present in `HF`. Due to which the boiling point of `HF` is higher and the volatility is less. Thus the volatility of hydrogen halides can be represented as
Volatility: `HClgtHBrgtHIgtHF`.