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Vapor-Liquid Equilibrium
GATE 2020
Medium
Mole fraction and activity coefficient of component 1 in a binary liquid mixture are x1 and γ1. GE is excess molar Gibbs energy, R is the gas constant, T is absolute temperature. Which one of the following is always true?
- lim(x1→1) GE/RT = 0
- Blim(x1→1) GE/RT = 0.5
- Clim(x1→1) γ1 = 0
- Dlim(x1→1) γ1 = 0.5
Explanation
Excess Gibbs energy must vanish at both pure-component limits (x1→0 and x1→1), since a pure substance has no mixing non-ideality. γ1→1 (not 0 or 0.5) as x1→1, by Raoult's law/Lewis-Randall convention.
Source: GATE CH 2020 (2020)
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