(a) Draw the structures of the following:

(i) H2S2O8                                     (ii) HClO4

(b) How would you account for the following:

(i) NH3 is a stronger base than PH3.

(ii) Sulphur has a greater tendency for catenation than oxygen.

(iii) F2 is a stronger oxidising agent than Cl2.

Concept Videos :-

#7 | 17th Group

Concept Questions :-

group 17 ,preparation and properties

(a)  (i) H2S2O8 (Peroxodisulphuric acid )or Marshall's acid :

(ii) HClO4 (Perchloric acid) :

(b) (i) Since both P and N contain lone pairs of electrons but due to small size and high electronegativity of Nitrogen in NH3, the electron density is much higher than PH3, therefore it can easily donate electrons and acts as strong Lewis base than PH3.

(ii) The greater catenation tendency of sulphur is due to two reasons :

(a) The lone pair of electrons feels more repulsion in O-O bond than S-S bond due to its small size and thus S-S forms strong bond.

(b) As the size of atom increases down the group from O-PO, the strength of bond increases and therefore catenation tendency also increases.

(iii) Due to low bond dissociation enthalpy and high electronegativity of Fluorine, it has strong tendency to accept electrons and thus get reduced.


Therefore F2 acts as strong oxidising agent, while Cl2 is weak oxidising agent due to low electronegativity.

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