Solutions — Chemistry STD 12 Science — Question

→ "Some liquids on mixing, from azeotropes which are binary mixtures having the same composition in liquid and vapour phase and boil at a constant temperature."
→ In such cases, it is not possible to separate the components by fractional distillation.
→ There are two types of azeotropes
(1) Minimum boiling azeotrope :
→ "The solutions which show is large positive deviation from Raoult's law form minimum boiling azeotrope at a specific composition."
→ For example, ethanol-water mixture (obtained by fermentation of sugars) on fractional distillation gives a solution containing approximately 95% by volume of ethanol. Once this composition, known as azeotrope composition, has been achieved, the liquid and vapour have the same composition, and no further separation occurs.
(2) Maximum boiling azeotrope:
→ "The solutions that show large negative deviation from Raoult's law form maximum boiling azeotrope at a specific composition."
→ Nitric acid and water is an example of this class of azeotrope. This azeotrope has the approximate composition, 68% nitric acid and 32% water by mass, with a boiling point of 393.5 K