Question

Which of the following azeotropic solutions has the boiling point less than boiling point of the constituents $A$ and $B$?

• A. $CHCl _{3}$ and $CH _{3} COCH _{3}$
• B. $CS _{2}$ and $CH _{3} COCH _{3}$
• C. $CH _{3} CH _{2} OH$ and $CH _{3} COCH _{3}$
• D. $CH _{3} CHO$ and $CS _{2}$

Answer 1

Answer: (C)

$CH _{3} CH _{2} OH$ and $CH _{3} COCH _{3}$

Answer 2

When the new interactions are weaker than those in the pure constituents, the boiling point of the resultant solution is less than that of the constituents. Such condition is found in case of non-ideal solution showing positive deviation from Raoult's law. Among the given, solution of $CH _{3} CH _{2} OH$ and $CH _{3} COCH _{3}$ is non-ideal and show positive deviation. Hence, it has lesser boiling point or higher vapour pressure.