List of top Chemistry Questions on d -and f -Block Elements asked in CBSE CLASS XII

Comment on the statement that elements of the first transition series possess many properties different from those of heavier transition elements.

Write down the electronic configuration of:
(i) Cr³⁺ (iii) Cu⁺ (v) Co²⁺ (vii) Mn²⁺ 
(ii) Pm³⁺ (iv) Ce⁴⁺ (vi) Lu²⁺ (viii) Th⁴⁺

Indicate the steps in the preparation of: 

1.  K₂Cr₂O₇ from chromite ore. 
2.  KMnO₄ from pyrolusite ore.

Name the oxometal anions of the first series of the transition metals in which the metal exhibits the oxidation state equal to its group number.

Name the members of the lanthanoid series which exhibit +4 oxidation state and those which exhibit +2 oxidation state. Try to correlate this type of behavior with the electronic configurations of these elements.

Give examples and suggest reasons for the following features of the transition metal chemistry: 

1. The lowest oxide of transition metal is basic, the highest is amphoteric/acidic.
2. A transition metal exhibits highest oxidation state in oxides and fluorides.
3. The highest oxidation state is exhibited in oxoanions of a metal.

What are the characteristics of the transition elements and why are they called transition elements? Which of the d-block elements may not be regarded as the transition elements?

What is meant by 'disproportionation'? Give two examples of disproportionation reaction in aqueous solution.

Predict which of the following will be coloured in aqueous solution? Ti³⁺ ,V³⁺ , Cu⁺ , Sc³⁺ , Mn²⁺ , Fe³⁺ and Co²⁺ . Give reasons for each.

For M²⁺/M and M³⁺/M²⁺ systems, the \(E^\ominus\) values for some metals are as follows: 
Cr²⁺/Cr -0.9V 
Cr³ /Cr²⁺ -0.4 V 
Mn²⁺/Mn -1.2V 
Mn³⁺/Mn²⁺ +1.5 V 
Fe²⁺/Fe -0.4V 
Fe³⁺ /Fe²⁺ +0.8 V 
Use this data to comment upon: 
(i) The stability of Fe³⁺ in acid solution as compared to that of Cr³⁺ or Mn³⁺ and 
(ii) The ease with which iron can be oxidised as compared to a similar process for either chromium or manganese metal.

Describe the preparation of potassium permanganate. How does the acidifiedpermanganate solution react with (i) iron(II) ions (ii) SO₂and (iii) oxalic acid? Write the ionic equations for the reactions.

Describe the oxidising action of potassium dichromate and write the ionicequations for its reaction with: (i) iodide (ii) iron(II) solution and (iii) H₂S

Describe the preparation of potassium dichromate from iron chromite ore.  What is the effect of increasing pH on a solution of potassium dichromate?

How is the variability in oxidation states of transition metals different from that of the non-transition metals? Illustrate with examples.

Explain giving reasons: 
 (i) Transition metals and many of their compounds show paramagnetic behaviour. 
 (ii) The enthalpies of atomisation of the transition metals are high. 
 (iii) The transition metals generally form coloured compounds. 
 (iv) Transition metals and their many compounds act as good catalyst.

What can be inferred from the magnetic moment values of the following complex species? 
Example Magnetic Moment (BM)
K₄[Mn(CN)₆] 2.2 
[Fe(H₂O)₆]²⁺ 5.3 
K₂[MnCl₄] 5.9

Write down the number of 3d electrons in each of the following ions: Ti²⁺, V²⁺, Cr³⁺, Mn²⁺, Fe²⁺, Fe³⁺, CO²⁺, Ni²⁺ and Cu²⁺ . Indicate how would you expect the five 3d orbitals to be occupied for these hydrated ions (octahedral).

Compare the general characteristics of the first series of the transition metals with those of the second and third series metals in the respective vertical columns. Give special emphasis on the following points: 

1. electronic configurations, 
2. oxidation states, 
3. ionisation enthalpies, and 
4. atomic sizes