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.
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.62Medium
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.63Medium
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.
Q.64Medium
Which of the following statements about diborane (B₂H₆) is incorrect?
Answer: C
B₂H₆ has a bridged structure with 3D geometry, not planar. It contains bridging hydrogens forming 3-center-2-electron bonds.
Q.65Easy
The standard electrode potential for Zn²⁺/Zn is -0.76 V. In a galvanic cell combining Zn and Cu electrodes, Zn will act as:
Answer: B
Zn has lower (more negative) reduction potential than Cu, making it more easily oxidized. It acts as the anode (negative electrode) in the galvanic cell.
Q.66Hard
The stability of peroxides increases in the order:
Answer: A
Larger cations better stabilize the larger O₂²⁻ ion through lattice energy considerations. K⁺ > Na⁺ > Li⁺, so K₂O₂ is most stable.
Q.67Hard
In the preparation of potassium permanganate from pyrolusite (MnO₂), the ore is first fused with KOH. The product formed is:
Answer: B
MnO₂ (Mn⁴⁺) is oxidized by air to MnO₄²⁻ (Mn⁶⁺) forming K₂MnO₄. This is then oxidized to KMnO₄ using oxidizing agents like Cl₂.
Q.68Easy
The primary use of zinc in brass alloy is to:
Answer: C
Zinc in brass (Cu-Zn alloy) enhances corrosion resistance through protective layer formation and improves cold-workability of copper.
Q.69Medium
The complex [Ni(CN)₄]²⁻ is diamagnetic. This indicates:
Answer: B
Ni²⁺ with strong field CN⁻ ligands shows diamagnetism (d⁸ with all paired electrons) in square planar geometry (dsp² hybridization).
Q.70Hard
The bond order between atoms in the superoxide ion O₂⁻ is:
Answer: B
O₂⁻ (superoxide) has configuration similar to O₂ with one additional electron in π* orbital. Bond order = (8-5)/2 = 1.5
Q.71Easy
Which of the following noble gases has the lowest ionization energy?
Answer: D
Ionization energy decreases down a group. Xenon (54 electrons) has the largest atomic radius and lowest ionization energy among noble gases listed.
Q.72Medium
In the preparation of chlorine by oxidizing HCl with MnO₂, the oxidation state of Mn changes from:
Answer: B
MnO₂ (Mn⁴⁺) acts as oxidizing agent, reducing Cl⁻ to Cl₂. Mn⁴⁺ gains 2 electrons, reducing to Mn²⁺.
Q.73Easy
The coordination number of Co in [Co(NH₃)₆]³⁺ complex is:
Answer: C
Coordination number is the number of ligands bonded to the central metal. Six NH₃ molecules surround Co³⁺, giving coordination number 6.
Q.74Medium
Which of the following factors does NOT affect the magnitude of crystal field splitting (Δ)?
Answer: C
Crystal field splitting depends on ligand strength, metal ion charge, and geometry, but NOT on the mass of the metal ion.
Q.75Hard
The reaction of concentrated H₂SO₄ with carbon produces primarily:
Answer: D
C + 2H₂SO₄(conc) → CO₂ + 2SO₂ + 2H₂O at 25°C. At higher temperatures: C + 2H₂SO₄(conc) → CO + 2SO₂ + 2H₂O, with CO and SO₂ in 1:1 ratio. Overall primary products are CO and SO₂.
Q.76Medium
Which of the following elements forms the most stable +6 oxidation state in its compounds?
Answer: C
Tungsten forms the most stable +6 oxidation state compounds like WO₃ and WCl₆. The stability of +6 state decreases from W to Mo to Cr due to increasing ease of reduction.
Q.77Easy
In the extraction of iron from haematite using blast furnace, the reducing agent is primarily:
Answer: A
CO produced in the blast furnace acts as the primary reducing agent for Fe₂O₃. Although coke is fed, CO generated from coke combustion performs the actual reduction.
Q.78Easy
The hybridization of sulphur in SF₆ molecule is:
Answer: C
SF₆ has 6 fluorine atoms bonded to sulphur with octahedral geometry. The hybridization is sp³d² involving d-orbitals from the third shell.
Q.79Medium
Which transition metal forms a complex with CO that has maximum carbonyl stretching frequency?
Answer: C
Manganese with lower electron density shows weaker back-bonding, resulting in higher CO stretching frequency. The order is Mn > Co > Fe > Ni based on back-bonding strength.
Q.80Easy
The aqueous solution of which salt is most acidic due to hydrolysis?
Answer: B
FeCl₃ undergoes significant hydrolysis: Fe³⁺ + H₂O ⇌ Fe(OH)²⁺ + H⁺. Fe³⁺ is a strong Lewis acid causing extensive hydrolysis and acidic solution.
