Question

Define maximum and minimum Boiling azeotropes.

Answer 1

Azeotropes Mixture:

• Azeotropic mixture is defined as a mixture of two or more liquids whose proportion cannot be altered or changed by simple distillation.
• It can have a lower boiling point or a higher boiling point.
• When azeotrope is boiled, producing the vapour and proportion of this constituent in this vapour and mixture boiling is not the same.
• Some compounds like Toulene, Benzene, and Cyclohexane form azeotropes with the mixture.
• Raoult's law states that the partial pressure of a solvent is equal to the vapour pressure of the pure solvent that is multiplied by its mole fraction.
• It is used as gas chromatographs, detectors, and columns.
  ${\mathrm{P}}_{\mathrm{solution}}={\mathrm{X}}_{\mathrm{solvent}}\times {\mathrm{P}}_{\mathrm{Solvent}}^{°}$
• where, ${\mathrm{P}}_{\mathrm{solution}}=$Vapour Pressure of Solvent, ${\mathrm{X}}_{\mathrm{solvent}}=$Mole Fraction of the solvent, and ${\mathrm{P}}_{\mathrm{solvent}}^{°}=$Vapor pressure of the solvent

Maximum Boiling Azeotropes or Negative Boiling:

• This solution from an ideal solution shows a negative deviation at a constant temperature.
• It shows a large negative deviation from Raoult's law.
• This mixture shows a boiling point higher than the boiling point.
• They exhibit lower vapour pressure and have the highest boiling point.
• These azeotropes boil higher than the boiling point${110}^{°}\mathrm{C}$.
• Example- Hydrogen chloride $\left(\mathrm{HCl}\right)$and water$\left({\mathrm{H}}_2\mathrm{O}\right)$.

Minimum boiling Azeotropes or Positive Boiling:

• This solution from an ideal solution shows a positive deviation at a constant temperature.
• These solutions are a positive deviation from Raoult's law.
• They show a boiling point lower than their constituent.
• They exhibit the highest vapour pressure and have the lowest boiling point.
• For example, a mixture containing Ethanol ($96\%$) and Water $\left(4\%\right)$ has a positive azeotrope.