CBSE Guess > Papers > Important Questions > Class XII > 2013 > Chemistry > Dand F block elements By Mr. R. Srinivas Vasudevamurthy

CBSE CLASS XII

Dand F block elements - 5 Marks Questions

Account for the following:

1. Zn, Cd and Hg are not considered as transition metals.

2. Cu,Ag &Au are considered as transition metal though it has 3d10 configuration.

3. Zn, Cd and Hg are volatile and Hg is a liquid metal.

4. Transition metals have high enthalpy of atomisation.

5. 4d and 5d elements have higher enthalpy of atomisation than 3d elements.

6. Density of 3d elements increases from Sc to Ni.

7. Atomic and ionic radii generally decrease along the period.

8. Zr and Hf have similar size.

9. Transition metals do not show regular variation of ionisation enthalpies.

10. 5d elements have higher ionisation enthalpy than 3d and 4d elements.

11. Generally first ionisation enthalpy increases along the period.

12. Cr &Cu has higher second ionisation enthalpy (Cr=24,Cu=29)

13. Mn &Zn has higher 3rd ionisation enthalpy (Mn=25 Zn=30)

14. Cu, Ni and Zn normally do not exhibit oxidation state higher than +2.

15. Transition metals show variable oxidation state.

16. Transition metals do not show regular variation of E⁰ values.

17. E⁰ Mn³⁺/ Mn²⁺ have higher +ve value than E⁰ Cr³⁺ / Cr²⁺.(Cr=24 Mn=25).

18. E⁰ Zn²⁺ / Zn has higher - value. ( Zn=30).

19. Transition metals form complexes easily.

20. Transition metals act as catalysts.

21. Transition metal compounds are paramagnetic.

22. Sc³⁺,Cu⁺ and Zn²⁺ are diamagnetic .Sc=21 Cu=29 Zn=30).

23. Oxidation state of transition metals increases by one unit.

24. E⁰ Ni²⁺ / Ni has higher - ve value.

25. Transition metal compounds are coloured.

26. Sc³⁺,Cu⁺ and Zn²⁺ are colourless .[Sc=21 Cu=29 Zn=30].

27. Transition metals form interstitial compounds easily.

28.  Transition metals form alloys easily.

29.   Higher oxides of transition metals are acidic.

30.  Enthalpy of atomization of transition metals reaches a maximum in the middle of each series

31.  Lanthanoid ions are coloured and paramagnetic.

32. La³⁺ and Lu³⁺ are colourless and diamagnetic. (La=57 Lu=71).

33. Ln are paramagnetic.

34.  La³⁺ is diamagnetic.

35. Ce is stable in +4 oxidation state. E0 Ce⁴⁺ / Ce³⁺  has higher positive value.

36. Eu²⁺ is a good reducing agent.(Eu=63).

37. Ce⁴⁺ is a good oxidising agent .

38. Yb²⁺ is stable. It acts as a reducing agent. (Yb=70).

39.  In lanthanoid hydroxide M(OH)3 basic character decreases with increase in atomic number.

40.  Actinoids show greater range of oxidation state than lanthanoids.

41.   Actinoid contraction is greater than lanthanoid contraction.

42.   Ionisation enthalpies of early actinoids are lesser than that of early lanthanoids.

43.   In the d4 species Mn³⁺ is an oxidising agent where as Cr²⁺ is a reducing agent

44.   Co(II) is stable in aqueous solution but get oxidised in the presence of complexing agents.

45.  d1 configuration is unstable in transition metals.

46. Transition metals exhibit higher oxidation state in oxides and flourides.

47. Zn has lowest enthalpy of atomisation.

48. First ionization enthalpy of Cr is lower while Zn is higher.(Cr=24, Zn=30)

49. Zn has lower second ionization enthalpy.

50. Number of oxidation states at the extreme ends of 3d transition metals are very few.

51. Transition metals in higher oxidation states are more stabilized in oxides than in fluorides.

52. E⁰ Cu²⁺ / Cu is positive.

53. E⁰ Sc³⁺ / Sc²⁺ has lower value (Sc=21)

54. E⁰ Zn³⁺ / Zn²⁺ have higher positive value.

55. E⁰ Fe³⁺ / Fe²⁺ has comparatively lower positive value than E⁰ Mn³⁺ / Mn²⁺ (Mn=25, Fe=26)

56. E⁰ V³⁺ / V²⁺ have lower negative value (V=23)

57. Cu²⁺ (aq) is more stable than Cu+ (aq) despite the d10 configuration of Cu+

58. Highest fluoride of Mn is MnF4 while highest oxide is Mn2O7.

59. Oxidising power of Oxides VO²⁺< Cr2O72- <MnO^4-

60. KMnO4 titration is not carried out using HCl as acid medium.

61. Third ionization enthalpy of La, Gd and Lu are abnormally low( La=57, Gd=64, Lu=71)

62. 5f electrons can take part in bonding to a greater extent than 4f electron though both have similar angular wave function.

63. Highest oxidation state is exhibited by oxoanion in transition metals.

64.  Generally negative value of E⁰ M²⁺ / M decreases across the series of 3d elements.

65. It is unsatisfactory to review the chemistry of actinoids in terms of oxidation state.

66.  Lower oxides of transition metal are basic while higher oxides are acidic.

67. Sc exhibits only one oxidation state.

68. Cr²⁺ is stronger reducing agent than Fe²⁺

69.  Mo(VI) and W(VI) are more stable than Cr(VI)

70. There is a greater horizontal similarity in the transition metals than in the main group elements.

71.  Nickel (II) does not form low spin octahedral complexes.

72. Transition elements form pi complexes.

73. There is more frequent metal-metal bonding in 4d and 5d transition elements.

 

1. What is lanthonoid contraction? What is the reason for lanthonoid  contraction? Mention the  consequences of  lanthonoid contraction.

2.  What is  mischmetal? Mention two uses of mischmetal.

3. How is

a) KMnO₄ prepared from pyrolusite ore?
b) K₂Cr₂O₇ prepared from chromite  ore?

4 . Write the ionic equations of the reactions involved when acidified KMnO₄ is treated with 

a) FAS solution
b) oxalic acid solution
c) hydrogen sulphide
d) KI solution
e) Sn²⁺solution
f) SO₃^2-
g) NO^2-
h) SO₂

5. Write the ionic equation of the reaction involved when alkaline KMnO4 is reacted with

a) KI solution.
b) S₂O₃^2-

6. Write the ionic equation of the reaction involved when acidified K2Cr2O7 reacts with

a) Sn²⁺ solution
b) SO₂
c) hydrogen sulphide
d) Fe²⁺

7. What is the effect of PH on chromate and dichromate solutions?

8. Compare the chemistry of lanthonoids and actinoids with reference to

a) electronic configuration
b) oxidation state
c) ionization enthalpy
d) chemical reactivity
e) magnetic behaviour
f) atomic size

9.  What is actinoid contraction? Why is it more pronounced than lanthonoid contraction?

10. Compare the general characteristic of first row transition metals with those of second and third series metals in the respective vertical columns with reference to

a) electronic configuration
b) oxidation state
c) ionization enthalpies
d) atomic size.

11. Compare the stability of +2 oxidation state for the elements of the 3d series.

12. Cr²⁺(aq) is a better reducing agent than Fe²⁺ despite the half filled stability of Fe³⁺ Why?

13. Which transition metal exhibit only one oxidation state. Why?

14. For M²⁺ / M and M³⁺ / M²⁺ systems E⁰ values of some metals are given below.

            Cr²⁺ / Cr        - 0.9V                     Cr³⁺ / Cr²⁺       - 0.4V 
            Mn²⁺ / Mn     - 1.2V                      Mn³⁺ / Mn²⁺    + 1.5V
            Fe²⁺ / Fe      - 0.4V                     Fe³⁺ / Fe²⁺      + 0.8V
            Use the data to comment upon:

a) Stability of Fe³⁺ in acid solution when compared to Cr³⁺ and Mn³⁺
b) ease with which iron can be oxidized as compared to chromium and manganese.

15. Outer electronic configuration of elements a) X= 4f1 5d1 6s2 b) Y=4f7 5d0 6s2 Determine the

a) atomic numbers of X and Y
b) Stable oxidation states of X and Y.
c) Which is an oxidizing agent and which is a reducing agent? Why?

16. Outer electronic configuration of element X is 5f⁷ 6d⁰ 7s² Determine the atomic number of the element. What is the stable oxidation state of this element?

17. Draw the structures of

a) manganate ion
b) permanganate ion
c) chromate ion and
d) dichromate ion.

18. What is disproportination   reaction? Give the reaction involving disproportination of 

a) Cu⁺ ion
b) MnO₄^2- ion.

19. Discuss the general properties of transition metals with reference to

a) electronic configuration
b) atomic radius
c) ionization enthalpy
d) oxidation state
e) magnetic behavior
f) colored compounds
g) complex formation
h) catalytic behavior
i) interstitial compounds
j) alloy formation
k) electrode potential (M²⁺ / M and M³⁺ / M²⁺k) stability of higher oxidation state

20. What are transition metals? Which three elements are not considered as transition metals though they are kept in d block? In which way the electronic configuration of transition element differ from non transition elements?

21. Compare the stability of +2 oxidation state of the elements with electronic configurations
3d⁶4s², 3d²4s⁵ and 3d³4s².

22. A colored compound A when fused with alkali gives a green colored compound B. B on Electrolysis gives a purple colored compound C. Identify the compounds. Write the reactions involved. Also write the equation of the reaction involved in the disproportination  reaction of B in acid medium.

23. Determine the number of  unpaired electrons in Mn²⁺ ion. Calculate the magnetic moment in  Bohr maneton unit.

24. Which transition element exhibit only one oxidation state? Why?

25. An element X has atomic number 58 and another element Y has atomic number 95.

a) Give the ground state electronic configuration of X and Y.
b) Give their stable oxidation state.
c) Is X an oxidizing or reducing agent? Why?
d) Is Yan oxidizing or reducing agent? Why?

26. In which way the variation in oxidation state of transition metal differ from representative elements?

Submitted By : Mr. R. Srinivas Vasudevamurthy
Email: [email protected]