Pure water boils at 100°C; pure ethanol at 78°C. A 0.5 mole fraction mixture under positive deviation will:
ABoil below 78 (minimum-boiling azeotrope possible)
BNot boil
CBoil between 78 and 100
DBoil above 100
Answer & Solution
Correct answer: A. Boil below 78 (minimum-boiling azeotrope possible)
Positive deviation: weaker mixture interactions, higher vapour pressure than ideal, LOWER boiling point. Can form minimum-boiling azeotrope (boiling below either pure component).
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