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CBSE Important Questions

CBSE Guess > Papers > Important Questions > Class XII > 2008 > Chemistry > Chemistry By Mr. S.Vasu

Chemistry

Q. 1. There is a considerable increase in covalent radius from N to P but from As to Bi only a small change is observed.

Q. 2. Ionisation enthalpy of group 15 elements is much higher than that of group 14 elements.

Q. 3. Ionic radius of Sb and Bi are very less when compared to the ionic radius of N,P and As.

Q. .4. Metallic character of group 15 elements decreases on going down the group.

Q. .5. Tendency to show – 3 oxidation states in group 15 decreases on going down the group.

Q. .6. Nitrogen can’t form penta halides.

Q. 7. Nitrogen exhibits bonding while heavier members exhibit bonding.

Q. 8. N2 is a gas while P4 is a solid.

Q. 9. Catenation tendency is weaker in nitrogen.

Q. 10. N2 molecule is chemically inert while white phosphorus is more reactive.

Q. 11. In group 15, +3 oxidation state is more stable than +5 oxidation state on going down the group .

Q. 12. R3 P=O is known but R3 N=O is unknown.

Q. 13. Basicity of hydrides NH3> PH3 > AsH3 > SbH3 > BiH3

Q. 14. Stability of hydrides NH3> PH3 > AsH3 > SbH3 > BiH3

Q. 15. Reducing character of hydrides NH3< PH3 < AsH3 < SbH3 <BiH3

Q. 16. The oxides in higher oxidation states of group 15 elements are more acidic than that of lower oxidation state.

Q. 17. Basicity of group 15 oxides increases on going down the group.

Q. 18. PCl5 is more covalent than PCl3.

Q. 19. PCl5 is more covalent than PF5.

Q. 20. All the five bonds in PCl5 are not equivalent.(Or) PCl5 is more reactive than PCl3.

Q. 21. Both PCl3 and PCl5 fumes in air.

Q. 22. PH3 has lower boiling point than NH3.

Q. 23. NH3 acts as a lewis base.

Q. 24. NO2 molecule dimerise to become N2O4.

Q. 25. Aluminium is rendered passive in concentrated HNO3.

Q. 26. Concentrated HNO3 becomes yellow when exposed to light.(Or) concentrated HNO3 is an oxidizing agent.

Q. 27. White phosphorus is more reactive than red phosphorus. Black phosphorus is least reactive.

Q. 28. Bond angle in PH3+ is higher than that of PH3.

Q. 29. HNH bond angle in NH3 is less than the tetra hedral bond angle of 109.50.

Q. 30. Bond angles of HPH,HAsH and HSbH are closer to 900.

Q. 31. H3PO4 is tri protic, H3PO3 is diprotic while H3PO2 is mono protic.

Q. 32. H3PO2 is a good reducing agent.

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

Q. 34. NO is an odd electron molecule but does not dimerise to give N2O2.

Q. 35. Sulphur has very high boiling and melting point when compared to oxygen.

Q. 36. In group 16 tendencies to show -2 oxidation state decreases on going down the group.

Q. 37. In group 16 +4 oxidation state become more stable than +6 oxidation state on going down the group.

Q. 38. Oxygen can show a maximum covalency of 4 and it can not form hexa valent compound.

Q. 39. Acidity of group 16 hydrides H2O <H2 S < H2Se < H2Te.

Q. 40. Reducing character of group 16 hydrides H2O <H2 S < H2Se < H2Te

Q. 41. Boiling point of H2O is higher than that of H2 S.

Q. 42. Sulphur exhibit +6 oxidation state when it combines with fluorine.

Q. 43. SF6 is exceptionally stable or it can not be hydrolysed easily.

Q. 44. SF6 is known while SCl6 is unknown.

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