Vapour pressure of a liquid-liquid solution
- Acetic acid in water is a liquid-liquid solution. Similarly lemon juice added to water for making lemonade is a liquid-liquid solution.
- Let two volatile components of a binary solution be expressed as 1 and 2.
- In a closed vessel both the components of the solution would evaporate and establish an equilibrium state between the vapour phase and the liquid phase.
- Let p total = Total vapour pressure
p1 = Partial vapour pressures of component 1
p2= Partial vapour pressures of component 2
x1 = Mole fractions of component 1.
x2 = Mole fractions of component 2
x1 = Mole fractions of component 1.
x2 = Mole fractions of component 2
- Dalton’s law of partial pressures states that the total pressure (ptotal) of the solution is the sum of the partial pressures of the components of the solution.
- Mathematically, P total = P1 + P2
- Substituting the values of p1 and p2 we get
- The minimum value of ptotal is p10 and the maximum value is p20, assuming that p10 < p20.
- Let y1 = Mole fractions of the component 1
y2 = Mole fractions of the component 2
According to Dalton’s law of partial pressures:
P1 = y1 Ptotal
P2 = y2 Ptotal
