A student attempts to obtain anhydrous ethanol by fractional distillation of a 60 % (by mass) ethanol–water solution at 1 atm. The ethanol–water system forms a minimum-boiling azeotrope at 78.2 °C that is 95 % (by mass) ethanol. Which of the following best describes the composition of the first few millilitres of distillate collected and the reason for it?
(a) About 95% ethanol, because the azeotrope vaporizes preferentially and cannot be further enriched by simple distillation.
(b) About 60% ethanol, because the distillate composition remains the same as the boiling liquid.
(c) About 80–90% ethanol, because ethanol's lower boiling point makes the vapour only moderately enriched.
(d) Nearly 100% ethanol, because repeated vaporisation–condensation removes all water in the first fraction.