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The effect of applied pressure on vapor pressure. The location of phase boundaries. Pressure and temperature at which two phases can coexist. There is a relation between dp and dT that ensures that the system remains in equilibrium as either variable is changed. Relation between dp and dT.
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The location of phase boundaries Pressure and temperature at which two phases can coexist. There is a relation between dp and dT that ensures that the system remains in equilibrium as either variable is changed.
Solid-Vapour Boundary 1 bar
Phase Rule F=C-P+2 C = number of component
Total number of intensive variable = pc +2 Mole fraction of components in each phase must be one Number of relation =number of phases= p For chemical equilibrium, Chemical potential of individual component will be same in each of the phases. In each of the component (p-1) relation for each of the component Total number of relation for chemical equilibrium = c(p-1) Degree of Freedom = pc + 2 – p - c(p-1) = c – p + 2
What happens to boiling point or freezing point of a liquid in the presence of a solute? What happens to chemical potential of a liquid in the presence of solute?
There is elevation of boiling point upon addition of a solute. There is depression of freezing point upon addition of a solute.
The depression of Freezing point Solubility Solutes with high melting points and large enthalpies of melting have low solubilities at normal temperature.
Two component liquid Systems F=C-P+2 F=4-P Maximum degree of freedom = 3 Temperature, pressure and composition.
Q. One mole of benzene is mixed with two moles of toluene. At 60 C , the vapor pressure of benzene and toluene are 51.3 and 18.5 kPa, respectively. (a) As the pressure is reduced, at what pressure will boiling begin? (b) What will be the composition of the first bubble of vapor?