The disproportionation of H₂O₂ in acidic medium is catalyzed by:
Answer: C
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.
Q.142Medium
The geometry of [PtCl₄]²⁻ complex is:
Answer: B
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.
Q.143Medium
The rate of precipitation of AgCl from a solution is fastest when:
Answer: D
Rapid mixing increases collision frequency. The presence of AgCl seed crystal provides nucleation sites. Both factors enhance precipitation rate by different mechanisms.
Q.144Medium
In aqueous solution, which ion hydrolyzes to the maximum extent?
Answer: B
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⁺.
Q.145Medium
The bond angle in PCl₃ molecule is approximately:
Answer: B
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.
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Q.146Medium
Which of the following compounds shows maximum lattice energy?
Answer: B
MgO has the highest lattice energy due to smallest cation (Mg²⁺) and anion (O²⁻) sizes combined with higher charges. Order: MgO > NaCl > CaO > KCl.
Q.147Medium
The ionization potential of beryllium is higher than boron because:
Answer: C
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.
Q.148Medium
When a solution of potassium permanganate is diluted with water in the presence of ethanol, the purple color fades. This is because:
Answer: C
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.
Q.149Medium
Which of the following lanthanide elements has the electronic configuration [Xe]4f⁷5d¹6s²?
Answer: A
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.
Q.150Medium
A metal X is more easily oxidized than metal Y. If X and Y form a galvanic cell, which metal acts as the anode?
Answer: A
The metal that is more easily oxidized (more reactive) acts as the anode. Metal X, being more reactive, loses electrons and acts as the anode (negative electrode).
Q.151Medium
The standard cell potential for a reaction is -0.5 V. What can be concluded about this reaction?
Answer: D
A negative E° (E°cell < 0) indicates a non-spontaneous reaction under standard conditions. ΔG° = -nFE°, so negative E° gives positive ΔG°.
Q.152Medium
In the Daniel cell, the half-cell potentials are: Cu²⁺ + 2e⁻ → Cu, E° = +0.34 V and Zn²⁺ + 2e⁻ → Zn, E° = -0.76 V. Calculate E°cell:
Answer: C
E°cell = E°cathode - E°anode = 0.34 - (-0.76) = 0.34 + 0.76 = 1.10 V. Cu²⁺ is reduced (cathode) and Zn is oxidized (anode).
Q.153Medium
Which of the following has the highest reduction potential?
Answer: A
Fluorine has the highest reduction potential among the halogens, approximately +2.87 V. Reduction potentials decrease down the halogen group: F₂ > Cl₂ > Br₂ > I₂.
Q.154Medium
What is the relationship between ΔG° and E°cell?
Answer: B
The Gibbs free energy change is related to cell potential by ΔG° = -nFE°cell, where n is the number of electrons transferred, F is Faraday's constant, and E° is the standard cell potential.
Q.155Medium
In electroplating of iron with copper, the cathode is made of:
Answer: B
In electroplating iron with copper, iron (the object to be plated) acts as the cathode where Cu²⁺ ions are reduced and deposit as copper metal. The anode is made of copper.
Q.156Medium
The conductivity of a solution decreases with dilution because:
Answer: C
Upon dilution, the number of ions per unit volume decreases (concentration effect) and ionic mobility also increases slightly due to reduced ion-ion interactions, but overall conductivity decreases because the decrease in ion concentration dominates.
Q.157Medium
What is the relationship between ΔG° and E°cell at 25°C?
Answer: A
The fundamental relationship is ΔG° = -nFE°cell, where n is number of electrons, F is Faraday constant (96485 C/mol), and E°cell is standard cell potential.
Q.158Medium
A cell has E°cell = +0.34 V. Which statement is correct?
Answer: C
When E°cell > 0, the cell reaction is spontaneous. ΔG° = -nFE°cell is negative, indicating spontaneity.
Q.159Medium
The molar conductivity of an electrolyte increases upon dilution because:
Answer: B
Upon dilution, the degree of ionization increases due to reduced ion-ion interactions (interionic forces), leading to more free ions and higher molar conductivity.
Q.160Medium
During the electrolysis of molten NaCl, the cathode product is:
Answer: B
In molten NaCl electrolysis, Na⁺ is reduced at cathode to Na metal. Cl⁻ is oxidized to Cl₂ at anode. Water is absent, so no oxygen evolution.
