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.
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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.
