CBSE Class 12 Chemistry HOTs - p – Block Elements

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CBSE Chemistry HOTs questions database with answers (Please refer to other links for answers to HOTs questions) for Class 12 of CBSE exams for CBSE Students. Based on CBSE and CCE guidelines. The students should practice these Question Papers to gain perfection which will help him to get more marks in CBSE examination. Please refer to more CBSE Class 12 question papers in other links. Please refer to more CBSE Class XII sample papers for SA 1/ SA 2, question papers, HOTs etc in other links.




1. PCl3 fumes in moist air. Why? 1

2. Oxides of P, As, Sb exist as dimers (P4O6, P4O10, As4O6, and As4O10). Why? 1

3. P4O10 is used as dehydrating agent. Why? 1

4. Oxygen and sulphur exhibit –2 oxidation state where as others (Se, Te) exhibit +2

oxidation states. 1

5. Chemical methods are not practicable for the preparation of Fluorine. 1

6. Why H2SO4 is not used for the preparation of HBr from NaBr 1

7. Iodine forms I3

- ion but F2 does not form F3

- ion. Why? 1

8. NH3 has a higher proton affinity than PH3. Explain 1

9. Bleaching of flowers by chlorine is permanent while that by sulphur dioxide is temporary. Why? 1

10. Why does chlorine water loses its yellow colour on standing? 1


11. Oxides of Nitrogen have open chain structure while those of phosphorous have closed chain or cage structure. Why is it so? Illustrate with one structural example for each type of oxide or the oxides of  phosphorous have cage structure but not open ones. 2

12. When a moist blue litmus paper is dipped in a solution of hypochlorous acid, it first turns red and then latter gets decolorized. Why? 2

13. Iodine is liberated when KI is added to a solution of Cu2+ ions but Cl2 is not liberated when KCl is added to a solution of Cu2+ ions. Why? Explain. 2

14. State the reasons

i. ClF3 exists but FCl3 does not

ii. BH4

- and NH4

+ are isoloble 2

15. Why is it important to add KF in HF and exclude moisture during electrolysis of HF for the preparation of Fluorine ? 2

16. Why SO2 is a better reducing agent in alkaline medium as compared to that in acidic medium ? Explain.

Please refer to the attached file for CBSE Class 12 Chemistry HOTs - p – Block Elements


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