Reasoning Questions in P Block Elements

1. Though nitrogen exhibits +5 oxidation state, it does not form pentahalide. Give reason. Ans: Nitrogen valence electronic configuration nsnp due to absence empty dorbitals, it can not extend its valence to 5 2. PH3 has lower boiling point than NH3. Why? Ans: Unlike NH3, PH3 molecules are not associated through hydrogen bonding in liquid state. That is why the boiling point of PH3 is lower than NH3. 3. Why are pentahalides more covalent than trihalides ? Ans: Higher the positive oxidation state of central atom, more will be its Polarizing power which, in turn, increases the covalent character of bond formed between the central atom and the other atom. 4. Why is BiH3 the strongest reducing agent amongst all the hydrides of Group 15 elements ? Ans: Among hidres of group 15 from NH3 to BiH3 as size of central atom Increases M—H bond strength decreases. Hence it act as strong reducing agent. 5. Write the reaction of thermal decomposition of sodium azide. Ans: 2 NaN3  2 Na + 3 N2(g) 6. Why is N2 less reactive at room temperature? Ans: Due to its high NN bond dissociation energy 7. Why does NH3 act as a Lewis base? Ans: Due to presence of one lone pair of electron present on Nitrogen 8. Mention the conditions required to maximize the yield of ammonia. Ans: Optimum Pressure & Optimum Temperature & Removal of ammonia by cooling. 9. How does ammonia react with a solution of Cu? Ans: Cu + 4 NH3  [Cu(NH3)4] and this is deep blue in color. 10. Why does NO2 dimerise ? Ans: Due to presence one odd electron on Nitrogen of NO2 11. What is the covalence of nitrogen in N2O5 ? Ans: Covalency is 4 because N is bonded with 4 bonds