NEET Chemistry The p-Block Elements (XII) Questions Solved


Give reasons for the following :

(i) Oxygen is a gas but sulphur is a solid.

(ii) O3 acts as a powerful oxidising agent.

(iii) BiH3 is the strongest reducing agent amongst all the hydrides of Group 15 elements.

(i) Due to small size and high electronegativity, oxygen forms pπ-pπ multiple bonds and thus forms diatomic. O2 molecule are held together by weak van der Waals forces of attraction which can be easily overcome by collisions at room temperature. Therefore O2 is gas at room temperature. On the other hand due to higher tendency for catenation and lower tendency for pπ-pπ multiple bonds, intra-atomic S8 has strong forces of attraction which cannot be overcome by collisions. Therefore S is solid at room temperature.

(iii) O3 is a powerful oxidising agent due to its high energy content than oxygen and hence decomposes to give diatomic oxygen and atomic oxygen

     O3gOzoneO2gDioxygen+OgAtomic oxygen

(iii) As we move down the group, the E-H bond length increases and their strength decreases. Bi-H bond is the weakest. It can break easily and evolves Ha2 gas which acts as the reducing agent.


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