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Topics in JEE Chemistry
In a electrochemical cell, the standard cell potential E°cell = 0.34 V. The value of ΔG° at 298 K is approximately: (F = 96500 C/mol)
Correct Answer:
B. -65.6 kJ/mol
EXPLANATION
ΔG° = -nFE°cell. For n=2 (typical): ΔG° = -2 × 96500 × 0.34 = -65,620 J/mol ≈ -65.6 kJ/mol.
The Henry's law constant for CO₂ in water at 25°C is approximately:
Correct Answer:
A. 1.67 × 10³ atm/(mol/L)
EXPLANATION
Henry's law constant for CO₂ in water at 25°C is Kh ≈ 1.67 × 10³ atm·L/mol, used as P = Kh·x.
For an ideal gas undergoing isothermal expansion, the work done by gas is:
Correct Answer:
B. nRT ln(Vf/Vi)
EXPLANATION
For isothermal process: W = nRT ln(Vf/Vi). Since Vf > Vi, work done by gas is positive.
The rate constant of a reaction at 25°C is k₁ and at 75°C is k₂. If Ea = 60 kJ/mol, what is k₂/k₁? (R = 8.314 J/mol·K)
Correct Answer:
C. 103
EXPLANATION
Using Arrhenius equation: ln(k₂/k₁) = (Ea/R)(1/T₁ - 1/T₂) = (60000/8.314)(1/298 - 1/348) ≈ 4.63, so k₂/k₁ ≈ 103.
At critical point, the compressibility factor Z equals:
Correct Answer:
C. 0.27
EXPLANATION
At the critical point, Z = PcVc/RTc = 0.27 for most real gases (theoretical value for van der Waals gas).