Home › Previous year questions › GATE 2019 CY › Question 60GATE 2019 CY – Question 60 Physical Chemistry · Phase Equilibria: Phase rule. Clausius- Clapeyron equation. Phase diagram of one component system: CO2, H2O, S; two component systems: liquid-vapor, liquid-liquid and solid-liquid systems. Fractional distillation. Azeotropes and Eutectics. · 2 marks · Numerical answer
A compound boils normally at 350 K and has temperature-independent vaporization enthalpy 30 kJ/mol. Find the pressure needed to boil it at 300 K in Torr (two decimal places). R=8.31 J/(mol K), 1 atm=760 Torr.
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Show answer and explanation Correct answer: 120.00 to 140.00
Explanation Integrated Clausius–Clapeyron gives $\ln(P_2/P_1)=-(\Delta H/R)(1/T_2-1/T_1)$. With P₁=760 Torr at 350 K, $P_2=760\exp[-30000(1/300-1/350)/8.31]\simeq136.21$ Torr. Lowering the boiling temperature requires reduced external pressure.
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