Question

Which of the following is/are true regarding maximum boiling azeotropes?

• A. $\Delta S_{mix}>0$
• B. $\Delta G_{mix}>0$
• C. Azeotropic mixture has higher vapour pressure as compared to vapour pressure of each component in pure state.
• D. $\Delta H_{mix}<0$

Answer 1

Answer: (A), (D)

$\Delta H_{mix}<0$

Maximum boiling azeotropes are those which boil at a higher temperature than the boiling point of each component in a pure state, e.g., 68 % nitric acid and 32 % water by mass.
Consequently, Azeotropic mixture has lower vapour pressure as compared to vapour pressure of each component in pure state.

Here,
$\Delta H_{mix}<0$
$\Delta V_{mix}<0$
$\Delta G_{mix}<0$
$\Delta S_{mix}>0$