CBSE 12th Chemistry D and F Block Important Questions 2025 For Exam Day

Ques 1

Explain briefly how the +2 state becomes more and more stable in the first half of the first-row transition elements with increasing atomic number.

Ques 2

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 catalysts.

Ques 3

What are interstitial compounds? Why are such compounds well-known for transition metals?

Ques 4

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

Ques 5

How would you account for the following:

(i) Of the d4 species, Cr2+ is strongly reducing while manganese(III)
is strongly oxidising.

(ii) Cobalt(II) is stable in aqueous solution but in the presence of
complexing reagents it is easily oxidised.

(iii) The d1 configuration is very unstable in ions.

Ques 6

Indicate the steps in the preparation of:
(i) K2Cr2O7 from chromite ore. (ii) KMnO4 from pyrolusite ore.

Ques 7

What are alloys? Name an important alloy which contains some of the lanthanoid metals. Mention its uses.

Ques 8

The chemistry of the actinoid elements is not as smooth as that of the lanthanoids. Justify this statement by giving some examples of the oxidation state of these elements.

Ques 9

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

Ques 10

What can be inferred from the magnetic moment values of the following complex species?

Example: K4[Mn(CN)6) [Fe(H2O)6]2+ K2[MnCl4]

Magnetic Moment (BM): 2.2 5.3 5.9