CBSE Class 12 Chemistry d and f block elements

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CBSE Class 12 Chemistry d and f block elements. Students can download these worksheets and practice them. This will help them to get better marks in examinations. Also refer to other worksheets for the same chapter and other subjects too. Use them for better understanding of the subjects.

d &f BLOCK ELEMENTS

1 MARK QUESTIONS (1-20)

1. Zn, Cd & Hg are not treated as true transition elements. Why?

2. Cu & Ag are transition metals although they have completely filled d-orbitals. Why?

3. Why some d-block elements have irregular (exceptional) electronic configuration?

4. Atomic size does not change appreciably in a row of transition metals. Why?

5. Transition elements have variable oxidation states. Why?

6. Transition metals have high melting and boiling points. Why?

7. Transition metals have high enthalpy of atomization. Why?

8. Transition metals show catalytic properties .Why?

9. Transition metals and their salts are generally colored .Why?

10. Why transition metals form coordination compounds?

11. Why transition metals form alloys?

12. Transition metals form interstial compounds. Why?

 

13. Zn, Cd & Hg have low boiling points and Hg is liquid. Why?

14. Transition metals and many of their compounds show paramagnetic behavior .Why?

15. d1 configuration is very unstable in ions .Why?

16. Cr2+ is strongly reducing while Mn3+ is strongly oxidizing. Why?

17. Cobalt(II) is stable in aqueous solution but in presence of complexing agents it gets oxidized. Why?

18. Mn2+ compounds are more stable than Fe2+ .Why?

19. Fe3+ is stable compared to Fe2+.Why?

20. Transition metals exhibit highest oxidation states in oxides and fluorides. Why?

2 Mark Questions (21-30)

21`.The highest oxidation state of transition metal is exhibited in oxoanions

For the first row transition metals the Eo values are:

Eo V Cr Mn Fe Co Ni Cu

(M2+/M) –1.18 – 0.91 –1.18 – 0.44 – 0.28 – 0.25 +0.34

Explain the irregularity in the above values.?

22. Why is the E0 value for the Mn3+/Mn2+ couple much more positive than that for Cr3+/Cr2+ or Fe3+/Fe2+?

Explain.?

23. In the series Sc (Z = 21) to Zn (Z = 30), the enthalpy of atomization of zinc is the lowest.Why?

24. Explain why Cu+ ion is not stable in aqueous solutions?

25 Actinoid contractions are greater from element to element than lanthanoid contraction.Why?

26. K2PtCl6 is well known compound and corresponding Ni4+ Salt isunknown . Whereas Ni+2 is more stable

than Pt+2.

27. Why KMnO4 is bright in colour ?

28. CrO is basic but Cr2O3 is amphoteric?

29. In the titration of Fe2+ ions with KMnO4 in acidic medium, why dil. H2SO4 is used and not dilHCl.

30. K2Cr2O7 is used as Primary Standard in volumetric analysis.Why?

3 MARKS QUESTIONS(31-40)

31. (a) Although Cu+ has configuration 3 d10 4 s0 (stable) and Cu2+ has configuration 3 d9 (unstable

configuration) still Cu2+ compounds are more stable than Cu+.

(b) Titanium (IV) is more stable than Ti (III) or Ti (II).

32. The actinoids exhibit more number of oxidation states and give their common oxidation states.

33. (a) Give reason CrO3 is an acid anhydride.

(b) Give the structure of CrO5.

34. Why is Cr2+ reducing and Mn3+ oxidising when both have d4 configuration ?

35. .(a) In MnO4

– ion all the bonds formed between Mn and Oxygen are covalent. Give reason.

(b) Beside + 3 oxidation state Terbium Tb also shows + 4 oxidation state. (Atomic no. = 65)

36. (a) Highest manganese flouride is MnF4 whereas the highest oxide is Mn2O7.

(b) Copper can not librate H2 from dil acids :

Note : Although only oxidising acids (HNO3 and hot conc. H2SO4) react with Cu light.

37. A metal which is strongly attracted by a magnet is attacked slowly by the HCl liberating a gas and

producing a blue solution. The addition of water to this solution causes it to turn pink, the metal is

38.Comment on the statement that elements of the first transition series possess many properties different

from those of heavier transition metal ?

39. The paramagnetic character in 3d-transition series elements increases upto Mn and then decreases.

Explain why?

40.Why are Mn2+ compounds more stable than Fe2+ compounds towards oxidation to +3 state?

5 MARK QUESTIONS(41-45)

41.A wellknown orange crystalline compound (A) when burnt impart violet colour to flame. (A) on treating

(B) and conc. H2SO4 gives red gas (C) which gives red yellow solution (D) with alkaline water. (D) on

treating with acetic acid and lead acetate gives yellow p. pt. (E). (B) sublimes on heating. Also on

heating (B) with NaOH gas (F) is formed which gives white fumes with HCl. What are (A) to (F) ?

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