A 200 mL liquid mixture contains (by volume) 60 % ethanol (CH3CH2OH), 30 % water, and 10 % propanone (acetone). At 1.00 atm, ethanol and water form a minimum-boiling azeotrope that distills at 78.2 °C with a composition of 95 % ethanol and 5 % water by mass. The normal boiling points of the pure liquids are: ethanol 78.4 °C, water 100.0 °C, and propanone 56.5 °C. The mixture is subjected to fractional distillation at 1.00 atm.
(a) Identify the composition of the first major fraction collected and explain your reasoning with reference to the data given.
(b) After the first fraction has been removed, two liquids remain in the distillation flask. Predict which liquid will distill next and describe the expected change (if any) in thermometer readings as this second fraction is collected.
(c) Propose one practical modification to the experimental conditions that could allow the laboratory to obtain ethanol of purity greater than 99 %. Explain the chemical principle that makes your modification effective.