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Vapor-Liquid Equilibrium
GATE 2017
Hard
The vapor pressure of a pure substance at temperature T is 30 bar. Actual g/RT for the saturated vapor at T,30bar is 7.0; ideal-gas g/RT is 7.7. The fugacity of the saturated liquid, rounded to 1 decimal place, is
14.9 bar(± 0.3 accepted)
Explanation
gR/RT=7.0−7.7=−0.7=ln(φ). φ_vapor=e^(−0.7)=0.4966. f_vapor=φ×P=0.4966×30=14.9 bar. Since liquid and vapor coexist, f_liquid=f_vapor=14.9 bar.
Source: GATE CH 2017 (2017)
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