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Laws of Thermodynamics
GATE 2020
Hard
The gas-phase reaction N2O4⇌2NO2 occurs isothermally/isobarically at 298K, 1.0 bar (ideal gas). ΔG°298=5253 J/mol, R=8.314 J/mol·K. Starting from 1 mole of pure N2O4, the fraction of N2O4 that decomposes at equilibrium is
- A0
- 0.17
- C0.38
- D1
Explanation
K=exp(−ΔG°/RT)=exp(−5253/2477.6)=exp(−2.1204)=0.120. With extent ξ: K=4ξ²/(1−ξ²)=0.12 ⟹ 4.12ξ²=0.12 ⟹ ξ²=0.02913 ⟹ ξ=0.17.
Source: GATE CH 2020 (2020)
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