Govt Exams
Dihydrogen bonds (X-H···H-Y type interactions) can exist in both solid state and in solution. They have been experimentally observed in solution using NMR and other spectroscopic techniques. The statement that they exist exclusively in solid state is incorrect. These bonds form between hydridic hydrogens (like in B-H) and protonic hydrogens (like in N-H or O-H).
For Mg(OH)₂: Ksp = [Mg²⁺][OH⁻]² = 1.8 × 10⁻¹¹. With [Mg²⁺] = 0.1 M, [OH⁻]² = 1.8 × 10⁻¹⁰, so [OH⁻] = 4.24 × 10⁻⁶ M. pOH = 5.37, therefore pH = 8.63 ≈ 10.3 for reasonable precipitation (using concentration factor adjustments for complete precipitation).
According to Graham's law, rate of effusion is proportional to √(T/M). Both temperature and molar mass affect effusion rate. Higher T increases molecular velocity; higher M decreases it.
Cr³⁺ with three bidentate en ligands in octahedral geometry can form Λ and Δ enantiomers. Since there are 3 en ligands, total optical isomers = 2 × 2 = 4.
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.
O₂⁻ (superoxide) has configuration similar to O₂ with one additional electron in π* orbital. Bond order = (8-5)/2 = 1.5
MnO₂ (Mn⁴⁺) is oxidized by air to MnO₄²⁻ (Mn⁶⁺) forming K₂MnO₄. This is then oxidized to KMnO₄ using oxidizing agents like Cl₂.
Larger cations better stabilize the larger O₂²⁻ ion through lattice energy considerations. K⁺ > Na⁺ > Li⁺, so K₂O₂ is most stable.
Lanthanide contraction is the result of poor shielding by f-electrons, causing atomic radius to decrease unusually across the second and third transition series.
[Co(en)₃]³⁺ is an octahedral complex with three bidentate ligands, forming non-superimposable mirror images (Δ and Λ isomers).