JEE Chemistry - MCQ Practice Questions

Both MnO₂ and Pt catalyze H₂O₂ decomposition to H₂O and O₂. MnO₂ is a heterogeneous catalyst while Pt can function as both heterogeneous and homogeneous catalyst.

Pt²⁺ is d⁸ with strong field Cl⁻ ligands. The dsp² hybridization gives square planar geometry, which is the preferred geometry for d⁸ complexes with strong field ligands.

Rapid mixing increases collision frequency. The presence of AgCl seed crystal provides nucleation sites. Both factors enhance precipitation rate by different mechanisms.

Be²⁺ has the smallest size and highest charge density, making it the strongest Lewis acid. It undergoes extensive hydrolysis. The order is Be²⁺ > Al³⁺ > Mg²⁺ > Ba²⁺.

PCl₃ has trigonal pyramidal geometry due to one lone pair on P. The bond angle is reduced from 120° (ideal trigonal) to 101.8° due to lone pair repulsion.

MgO has the highest lattice energy due to smallest cation (Mg²⁺) and anion (O²⁻) sizes combined with higher charges. Order: MgO > NaCl > CaO > KCl.

Be (1s² 2s²) has a filled 2s orbital which is more stable. Additionally, smaller size means electrons are closer to nucleus. Both factors increase ionization potential.

Permanganate ions (MnO₄⁻) oxidize ethanol to acetaldehyde and are themselves reduced to colorless Mn²⁺ ions (or MnO₂ depending on pH), causing the purple color to fade. This is a classic redox reaction where the oxidation state of Mn changes from +7 to +2.

Gadolinium has atomic number 64 with configuration [Xe]4f⁷5d¹6s². The half-filled 4f⁷ configuration makes Gd exceptionally stable. This is the only lanthanide with a 5d electron, making it unique among the lanthanide series.