Important Questions Chemistry Class XII

11/29/2011 CBSE

Q. 1. Both PCl3 and PCl5 fumes in air.

Q. 2. PH3 has lower boiling point than NH3.

Q. 3. NH3 acts as a lewis base.

Q. 4. NO2 molecule dimerise to become N2O4.

Q. 5. Aluminium is rendered passive in concentrated HNO3.

Q. 6. Concentrated HNO3 becomes yellow when exposed to light.(Or)
concentrated HNO3 is an oxidizing agent.

Q. 7. White phosphorus is more reactive than red phosphorus. Black phosphorus is
least reactive.

Q. 8. Bond angle in PH3+ is higher than that of PH3.

Q. 9. HNH bond angle in NH3 is less than the tetra hedral bond angle
of 109.50.

Q. 10. Bond angles of HPH,HAsH and HSbH are closer to 900.

Q. 11. H3PO4 is tri protic, H3PO3 is
diprotic while H3PO2 is mono protic.

Q. 12. H3PO2 is a good reducing agent.

Q. 33. H3PO2 is a stronger reducing agent than H3PO3.

Q. 14. NO is an odd electron molecule but does not dimerise to give N2O2.

Q. 15. Sulphur has very high boiling and melting point when compared to oxygen.

Q. 16. In group 16 tendencies to show -2 oxidation state decreases on going down
the group.

Q. 17. In group 16 +4 oxidation state become more stable than +6 oxidation state
on going down the group.

Q. 18. Oxygen can show a maximum covalency of 4 and it can not form hexa valent

Q. 19. Acidity of group 16 hydrides H2O2 S <>2Se <>2Te.

Q. 20. Reducing character of group 16 hydrides H2O2 S <>2Se <>2Te

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