d- & f-Block Elements: Class 12 Previous Year Questions

d- & f-Block Elements questions asked in CBSE board exams

Repeated questions first. Open the free app to see each question as it appeared in the paper, with its marking scheme.

1. (a) Complete and balance the following equations : 2 + 1 (i) 2KMnO4      K 513 (ii) Na2Cr2O7 + 2KCl –– (b) Why is it difficult to separate lanthanoid elements in pure state ?
   Board 20263 marksshort answer
2. (a) (i) From the given data of E values, answer the following questions : 3 + 2 E M2+/M V Cr Mn Fe Co Ni Cu –1.18 –0.91 –1.18 –0.44 –0.28 –0.25 +0.34 (I) Why E M2+/M show irregular trend in the above values ? (II) Why is E Cu2+/Cu value exceptionally posit…
   Board 20265 markslong answer
3. (a) First ionization enthalpy of Cr is lower than that of Zn. Why ? 1 + 1 (b) Mention any one property of the transition elements which makes them good catalysts.
   Board 20262 marksshort answer
4. Assertion (A) : Zinc, cadmium and mercury are not considered as transition elements. 1 Reason (R) : These elements have completely filled orbitals in their ground state as well as in their common oxidation states. { } 10 15.  (A) :   …
   Board 20261 markAssertion-Reason
5. Assertion (A) : Actinoids show wide range of oxidation states. 1 Reason (R) : Actinoids are radioactive in nature.
   Board 20261 markAssertion-Reason
6. Complete and balance the following chemical equations : 3×1 MnO + C,0°-+H+- (a) Heat (b) KMnO4 513 K Cr,02 (c) 2- +H,S + H+-
   Board 20253 marksshort answer
7. The elements of 3d transition series are given as : (1 + 1 + 1 = 3) Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn Answer the following : (a) Copper has exceptionally positive EM2+M value, why ? (b) Which element is a strong reducing agent in +2 oxidation state and why…
   Board 20253 marksshort answer
8. Examine the following observations : 2×1 (a) Transition elements generally form coloured compounds. (b) Zinc is not regarded as a transition element.
   Board 20252 marksshort answer
9. (a) (i) Account for the following : (1) The melting and boiling points of Zn, Cd and Hg are low. (2) Of the d4 species, Cr2+ is strongly reducing while Mn3+ is strongly oxidizing. (3) E o value of Cu2+/Cu is + 0·34 V. (ii) Complete and balance the following ch…
   Board 20245 markslong answer
10. Which one of the following first row transition elements is expected to have the highest third ionization enthalpy ? (A) Iron (Z = 26) (B) Manganese (Z = 25) (C) Chromium (Z = 24) (D) Vanadium (Z = 23)
    Board 20241 markMCQ
11. (a) What is lanthanoid contraction ? Actinoid contraction is greater from element to element than lanthanoid contraction. Why ? 1+1=2 OR (b) Why do transition metals have high enthalpy of atomization ? Which element of 3d-series has lowest enthalpy of atomizat…
    Board 20242 marksshort answer
12. Assertion (A) : Separation of Zr and Hf is difficult. Reason (R) : Zr and Hf have similar radii due to lanthanoid contraction.
    Board 20241 markAssertion-Reason
13. When MnO2 is fused with KOH in air, it gives : (A) KMnO4 (B) K2MnO4 (C) Mn2O7 (D) Mn2O3
    Board 20241 markMCQ
14. Assertion (A) : Copper is a non-transition element. 1 Reason (R) : Copper has completely filled d-orbitals in its ground state.
    Board 20231 markAssertion-Reason
15. SECTION – E 33. (a) (I) Account for the following : 3 + 2 (i) Eo value for Mn3+/ Mn2+ couple is much more positive than that for Cr3+/ Cr2+. (ii) Sc3+ is colourless whereas Ti3+ is coloured in an aqueous solution. (iii) Actinoids show wide range of oxidation s…
    Board 20235 markslong answer
16. Which of the following characteristics of transition metals is associated with their catalytic activity ? 1 (a) Paramagnetic nature (b) Colour of hydrated ions (c) High enthalpy of atomisation (d) Variable oxidation states
    Board 20231 markMCQ
17. M / 2 M E Cr Mn Fe Co Ni Cu Zn 0·91 1·18 0·44 0·28 0·25 + 0·34 0·76 From the given E values of the first row transition elements, answer the following questions : 3 1=3 (i) Why is Mn / 2 Mn E value highly negative as compared to other elements ? (ii) What is t…
    Board 20221 markvery short
18. (a) Account for the following : (i) Transition elements have higher enthalpies of atomisation. (i) Separation of a mixture of Lanthanoid elements is difficult. (ii) The E°m2+/M value for copper is positive. 1 ×3=3 OR (b) Define transition elements. Which of th…
    Board 20221 markvery short
19. Account for the following : 3 1=3 (i) Transition metals and their compounds show catalytic activities. (ii) Zn, Cd and Hg are non-transition elements. (iii) Zr and Hf are of almost identical atomic radii. IÊS> J
    Board 20221 markvery short
20. Following ions of 3d-transition series are given : Ti4+, V3+, Cr3+, Mn3+ (Atomic number : Ti= 22, V = 23, Cr = 24, Mn = 25) Identify the ion which is (i) most stable in aqueous solution. (ii) a strong oxidising agent. (ii) colourless in aqueous solution. Give …
    Board 20221 markvery short

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