Concept:Fractional distillation of a water-ethanol mixture reaches a thermodynamic limit due to azeotrope formation.
Formula:Not applicable to this conceptual question.
Solution:- When ethanol is distilled, it forms a constant-boiling (azeotropic) mixture with water at a concentration of 95.6% ethanol and 4.4% water.
- Because this mixture boils at a lower temperature (78.1°C) than pure ethanol (78.3°C), simple distillation cannot purify it further.
- This standard, commercially distilled \(\approx\) 95% ethanol mixture is universally termed rectified spirit.
Why other options are incorrect:100% ethanol is called absolute alcohol (requiring special drying agents like CaO to break the azeotrope). 85% and 90% are arbitrarily lower concentrations.
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