Which of the following statements are true for azeotropes?
A. Azeotropes are binary mixtures having same composition in liquid and vapour phase and boil at a constant temperature.
B. The solutions which show a large positive deviation from Raoult’s law form maximum boiling azeotrope at a specific composition.
C. 95% by volume of ethanol (ethanol-water mixture) is an example of minimum boiling azeotrope.
D. A solution of 68% nitric acid and 32% water by mass is an example of maximum boiling azeotrope.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → A, C and D only
A. Azeotropes are binary mixtures having same composition in liquid and vapour phase and boil at a constant temperature. — Correct. This is the definition of an azeotrope.
B. The solutions which show a large positive deviation from Raoult’s law form maximum boiling azeotrope at a specific composition. — Incorrect. A large positive deviation raises the vapour pressure and gives a minimum boiling azeotrope; a maximum boiling azeotrope comes from a large negative deviation.
C. 95% by volume of ethanol (ethanol-water mixture) is an example of minimum boiling azeotrope. — Correct. Ethanol-water shows a large positive deviation, and fractional distillation cannot take ethanol beyond about 95% by volume.
D. A solution of 68% nitric acid and 32% water by mass is an example of maximum boiling azeotrope. — Correct. Nitric acid-water shows a large negative deviation; this azeotrope boils at about 393.5 K, above both components.
NCERT (2026-27 edition):
Non-ideal Solutions – …
