The orange color arises from charge transfer between oxygen and chromium, not from d-d transition within Cr³⁺.
Q.227Medium
Which of the following metals can displace hydrogen from dilute acids?
Answer: C
Zn is more reactive than hydrogen and can displace it from dilute acids. Cu, Ag, and Au are less reactive than hydrogen.
Q.228Medium
The aqueous solution of which salt would be basic?
Answer: C
Na₂CO₃ solution is basic because CO₃²⁻ hydrolyzes to produce OH⁻ ions. It's the salt of weak acid and strong base.
Q.229Medium
Which complex ion shows maximum paramagnetism?
Answer: C
[CoF₆]³⁻ is high spin with 4 unpaired electrons (d⁶). [Fe(CN)₆]⁴⁻ is low spin with 0 unpaired electrons. [Fe(H₂O)₆]²⁺ has 4 unpaired electrons but [CoF₆]³⁻ has higher magnetic moment.
Q.230Medium
The lattice energy of NaCl is higher than that of NaI because:
Answer: B
Lattice energy is inversely proportional to interionic distance. Cl⁻ is smaller than I⁻, so NaCl has higher lattice energy.
Q.231Hard
The stability of peroxides and superoxides of alkali metals increases with increasing atomic number because:
Answer: A
Larger alkali metal cations (K⁺, Rb⁺) can stabilize larger peroxide and superoxide anions due to better lattice energy matching.
Q.232Hard
In the extraction of iron from Fe₂O₃ using CO as reducing agent, the rate-determining step involves:
Answer: B
In solid-state reduction, diffusion through the ash layer is often the rate-determining step, creating a diffusion barrier.
Q.233Hard
Which of the following chromium compounds would show maximum paramagnetic behavior?
Answer: A
[Cr(H₂O)₆]³⁺ is high spin with 3 unpaired electrons. CN⁻ is strong field ligand causing pairing. [Cr(NH₃)₆]³⁺ is intermediate.
Q.234Hard
The structure of [PtCl₄]²⁻ is square planar because:
Answer: D
Pt²⁺ has d⁸ configuration. With strong field Cl⁻, square planar geometry provides maximum CFSE and is thermodynamically favored.
Q.235Medium
Which of the following elements forms the most stable +6 oxidation state compound?
Answer: B
Molybdenum forms very stable +6 oxidation state compounds like MoO₃ and MoO₄²⁻. This is due to d-block stability and orbital availability.
Q.236Easy
In the thermite reaction, which metal is oxidized?
Answer: C
In the thermite reaction (2Al + Fe₂O₃ → Al₂O₃ + 2Fe), aluminum is oxidized from 0 to +3 oxidation state as it reduces Fe₂O₃.
Q.237Medium
Which halide of boron exists as a dimer in the gaseous state?
Answer: B
BCl₃ forms a dimer (B₂Cl₆) in gaseous state due to bridging chlorine atoms. BF₃ remains monomeric due to strong B-F bonds and p-p repulsion.
Q.238Easy
What is the coordination number of zinc in [Zn(CN)₄]²⁻?
Answer: B
Zinc has a coordination number of 4 in this complex as four cyanide ligands are bonded to it. This follows the typical tetrahedral geometry for Zn²⁺.
Q.239Medium
The hybridization of sulfur in SF₆ is:
Answer: C
SF₆ has 6 bonding pairs and 0 lone pairs on S. Coordination number = 6, requiring sp³d² hybridization with octahedral geometry.
Q.240Medium
Which compound shows the phenomenon of disproportionation?
Answer: C
H₂O₂ disproportionates: H₂O₂ → H₂O + ½O₂. NaClO: 3ClO⁻ → 2Cl⁻ + ClO₃⁻. Both show disproportionation.
