AIPMT PRELIMS2010Chemistry-Thermodynamics
AIPMT PRELIMS 2010 Chemistry Entropy and Gibbs Free Energy MCQ Question
Type: MCQ-numerical-Medium-Class 11
Standard entropies of X₂, Y₂ and XY₃ are 60, 40 and 50 JK⁻¹mol⁻¹ respectively. For the reaction 1/2 X₂ + 3/2 Y₂ → XY₃, ΔH = -30 kJ to be at equilibrium, the temperature should be
A
500 K
B
750 K
C
1000 K
D
1250 K
Correct Answer
Option B
Detailed Explanation
Using the Gibbs free energy equation ΔG = ΔH - TΔS and setting ΔG = 0 for equilibrium, we find T = ΔH/ΔS. The entropy change ΔS =⁵⁰⁻ (1/2 × 60 + 3/2 × 40) = -30 JK⁻¹mol⁻¹. Thus, T = 30,000/30 = 1000 K.
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