Chemistry carries the highest scoring potential in JEE for anyone who keeps the three branches separate in revision. This set covers physical chemistry numericals, organic reaction mechanisms and named reactions, and inorganic chemistry including periodic trends, chemical bonding and coordination compounds. Organic questions show the mechanism arrow by arrow, so the reasoning transfers to reactions you have not seen before.
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.
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.
