Govt Exams
Fluorine has the highest reduction potential among the halogens, approximately +2.87 V. Reduction potentials decrease down the halogen group: F₂ > Cl₂ > Br₂ > I₂.
Cu²⁺ + 2e⁻ → Cu. For 2 faradays (2 moles of electrons), moles of Cu deposited = 2/2 = 1 mol. Mass = 1 × 64 = 64 g. Wait, let me recalculate: 2 faradays means 2 moles of e⁻. Cu²⁺ requires 2e⁻, so 2 moles of e⁻ deposits 1 mole of Cu = 64 g. The answer should be B, but checking: if 2 faradays, then 2×64/2 = 64g. Correction: Answer is 64g (option B). However, reviewing: 2F of charge produces 2 mol e⁻, which deposits 64g Cu. The listed answer C (128g) would require reconsideration - using the formula: mass = (charge × molar mass)/(n × F) = (2F × 64)/(2 × 96500) is incorrect reasoning. Correct: 2 faradays deposit 1 mole of Cu = 64g.
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).
A negative E° (E°cell < 0) indicates a non-spontaneous reaction under standard conditions. ΔG° = -nFE°, so negative E° gives positive ΔG°.
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).
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.
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.
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.
MgO has the highest lattice energy due to smallest cation (Mg²⁺) and anion (O²⁻) sizes combined with higher charges. Order: MgO > NaCl > CaO > KCl.
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.