Class 12 Chemistry 2025 Board Exam

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

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

Two among the three components of DNA are β-D-2-deoxyribose and a heterocyclic base. The third component is :
(A) Adenine
(B) Phosphoric acid
(C) Sulphuric acid
(D) Uracil

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

Ligand EDTA₄– is an example of a :
(A) Monodentate ligand
(B) Didentate ligand
(C) Tridentate ligand
(D) Polydentate ligand

The coordination number of Co in [Co(en)₃]³⁺ is :
(A) 3
(B) 4
(C) 5
(D) 6

The type of isomerism shown by the complex [CoCl₂(en)₂]⁺ is :
(A) Linkage isomerism
(B) Geometrical isomerism
(C) Coordination isomerism
(D) Ionization isomerism