d- and f-Block Elements — Class 12 Chemistry PYQs

When MnO₂ is fused with KOH in air, it gives :
(A) KMnO₄
(B) K₂MnO₄
(C) Mn₂O₇
(D) Mn₂O₃

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)

The most stable oxidation state of Iron is :
(A) + 2
(B) + 3
(C) + 4
(D) – 2

The product of oxidation of SO₃²⁻ with MnO₄⁻ in acidic medium is :
(A) SO₂
(B) SO₄²⁻
(C) S₂–
(D) S₂O₃²⁻

The correct order for the increasing oxidizing power in 3d series of transition elements is :
(A) MnO₄⁻ < Cr₂O₇²⁻ < VO₂ +
(B) Cr₂O₇²⁻ < VO₂ + < MnO₄⁻
(C) VO₂ + < Cr₂O₇²⁻ < MnO₄⁻
(D) VO₂ + < MnO₄⁻ < Cr₂O₇²⁻

The equilibrium Cr₂O₇²⁻ ⇌ 2CrO₄²⁻ :
(A) exists in basic medium
(B) exists in acidic medium
(C) exists in neutral medium
(D) does not exist

Assertion (A) : Separation of Zr and Hf is difficult.
Reason (R) : Zr and Hf have similar radii due to lanthanoid contraction.
(A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
(B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
(C) Assertion (A) is true, but Reason (R) is false.
(D) Assertion (A) is false, but Reason (R) is true.

Assertion (A) : Transition metals have high enthalpy of atomization.
Reason (R) : This is because transition metals have low melting points.
(A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
(B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
(C) Assertion (A) is true, but Reason (R) is false.
(D) Assertion (A) is false, but Reason (R) is true.

Assertion (A) : Zr and Hf are radioactive.
Reason (R) : Zr and Hf have similar radii due to lanthanoid contraction.
(A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
(B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
(C) Assertion (A) is true, but Reason (R) is false.
(D) Assertion (A) is false, but Reason (R) is true.

(a) What is lanthanoid contraction ? Actinoid contraction is greater from element to element than lanthanoid contraction. Why ?

OR

(b) Why do transition metals have high enthalpy of atomization ? Which element of 3d-series has lowest enthalpy of atomization ?