The magnetic moment of [Fe(CN)₆]⁴⁻ is approximately:
Answer: A
CN⁻ is a strong field ligand causing pairing in d-orbitals. Fe²⁺ becomes diamagnetic with μ = 0 B.M. (t₂g⁶eg⁰ configuration).
Q.242Easy
Which metal exhibits variable oxidation states primarily due to incomplete d-orbital filling?
Answer: B
Iron (Fe) exhibits variable oxidation states (+2 and +3) due to its incomplete d-orbitals, allowing electron transitions between different oxidation states.
Q.243Medium
In the extraction of copper using electrorefining, what is the anode material?
Answer: B
Blister copper (impure copper from smelting) acts as the anode. Pure copper is the cathode. Impurities fall as anode mud.
Q.244Medium
Which of the following is a non-stoichiometric compound?
Answer: B
Fe₀.₉₅O is a non-stoichiometric compound with variable composition. It contains both Fe²⁺ and Fe³⁺ ions due to defects in crystal structure.
Q.245Easy
The white precipitate formed when AgNO₃ is added to a solution containing Cl⁻ ions is:
Answer: B
AgCl is a white precipitate (Ksp = 1.8 × 10⁻¹⁰) formed due to the low solubility product of silver chloride.
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Q.246Hard
Which of the following complexes would show optical isomerism?
Answer: B
[Co(en)₃]³⁺ is an octahedral complex with three bidentate ligands, forming non-superimposable mirror images (Δ and Λ isomers).
Q.247Easy
The ionization energy generally increases across a period because:
Answer: B
Across a period, increasing nuclear charge more significantly affects ionization energy than the slight increase in shielding, causing IE to increase.
Q.248Medium
Which statement about borax is correct?
Answer: B
Borax is a complex borate with formula Na₂B₄O₅(OH)₄·8H₂O, containing both triangular BO₃ and tetrahedral BO₄ units.
Q.249Hard
In the context of transition metals, what does the term 'lanthanide contraction' refer to?
Answer: D
Lanthanide contraction is the result of poor shielding by f-electrons, causing atomic radius to decrease unusually across the second and third transition series.
Q.250Easy
Which halogen has the lowest electronegativity?
Answer: D
Iodine has the lowest electronegativity among halogens (2.5) due to its largest atomic radius and furthest valence electrons from nucleus.
Q.251Medium
The reduction potential of Fe³⁺/Fe²⁺ is +0.77 V. This indicates:
Answer: C
Positive E° means Fe³⁺ is easily reduced and Fe²⁺ is easily oxidized. Fe³⁺ is a strong oxidizing agent relative to Fe²⁺.
Q.252Easy
Which of the following compounds would exhibit hydrogen bonding?
Answer: B
HF exhibits hydrogen bonding between H (bonded to highly electronegative F) and lone pairs on F of adjacent molecules.
Q.253Easy
Which of the following d-block elements has the configuration [Ar]3d⁵4s¹?
Answer: A
Chromium has the electronic configuration [Ar]3d⁵4s¹ due to half-filled d-orbital stability, making it more stable than [Ar]3d⁴4s².
Q.254Medium
The spin-only magnetic moment of Fe²⁺ in its ground state is approximately:
Answer: B
Fe²⁺ has 4 unpaired electrons (d⁶ configuration). Magnetic moment = √[n(n+2)] = √[4×6] = 4.90 BM
Q.255Easy
Among the following oxides, which one is amphoteric?
Answer: B
Al₂O₃ reacts with both strong acids and strong bases, exhibiting amphoteric character. MgO is basic, Na₂O is strongly basic, and Cl₂O₇ is acidic.
Q.256Easy
In the extraction of iron from haematite using blast furnace, carbon monoxide acts as:
Answer: A
CO reduces Fe₂O₃ to Fe by accepting oxygen: Fe₂O₃ + 3CO → 2Fe + 3CO₂. CO is the primary reducing agent at higher temperatures.
Q.257Medium
The crystal field splitting energy (Δ) for [Co(H₂O)₆]²⁺ is approximately 9,300 cm⁻¹. The complex will be:
Answer: A
Co²⁺ is d⁷. Water is a weak field ligand with small Δ, resulting in high spin configuration (t₂g⁵ eg²) with 4 unpaired electrons.
Q.258Medium
Which of the following lanthanides has the configuration [Xe]4f⁷6s²?
Answer: A
Europium (Eu) has atomic number 63 and configuration [Xe]4f⁷6s², with a half-filled f-orbital making it particularly stable.
Q.259Medium
The solubility product of AgCl at 25°C is 1.8 × 10⁻¹⁰. In 0.1 M NaCl solution, the concentration of Ag⁺ will be:
Answer: A
Ksp = [Ag⁺][Cl⁻] = 1.8 × 10⁻¹⁰. With [Cl⁻] = 0.1 M, [Ag⁺] = Ksp/[Cl⁻] = 1.8 × 10⁻¹⁰/0.1 = 1.8 × 10⁻⁹ M
Q.260Medium
The geometry of [PdCl₄]²⁻ complex is:
Answer: B
Pd²⁺ is d⁸ with strong field preference. It forms square planar geometry with Cl⁻ (weak field ligand) due to crystal field stabilization.
