# Give reasons for the following(a) $NO_{2}$ dimerises readily.(b) Chlorine acts as bleaching agent.(c) In spite of small size, electron gain enthaply of oxygen is less negative as compared to sulphur.(d) Unlike chlorine, fluorine forms only one oxaacid, HOF.(e) Noble gas has very low boiling points.

(a) NO2 contains an unpaired electron that makes it reactive and hence it dimerizes to form a more stable N2O4.

(b) Chlorine gas in the presence of moisture reacts with water molecules to form hydrochloric acid and hypochlorous acid. Hypochlorous acid being reactive readily dissociate to generate nascent oxygen. Hence chlorine acts as bleeching agent.

$Cl_{2}+H_{2}O\rightarrow HCl+HOCl$

$HOCl\rightarrow HCl + [O]$

(c) The larger is the force between the nucleus and the incoming electron, the larger negative is the electron gain enthaply. In case of oxygen, the size of atom is so small that an incoming electron experienceslarger electron replusion as compared to nuclear attraction of sulphur is higer and hence electron gain enthaply of oxygen is less negative as compared to that of sulphur.

(d) Due to small size and high electronegativity, fluorine cannot form multiple oxyacids unlike chlorine. Multiple oxygen atoms around fluorine get sterically hinderd.

(e) Noble gas have completely filled outermost shell and hence it becomes difficult for them to form intermolecular bond. Thus, they have low boiling point.

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