At a mountaintop laboratory where the atmospheric pressure is 0.80 atm
CHEMISTRY · Single correct · A Level · Chemistry · Alkanes · Alkanes
Problem
At a mountaintop laboratory where the atmospheric pressure is 0.80 atm, a chemist distills an equimolar mixture of water and propanone (acetone). The normal boiling points at 1.0 atm are 100 °C for water and 56 °C for propanone. Which of the following best predicts the order in which the two components will be collected and explains why?
(a) Water will be collected first because decreasing the external pressure lowers water’s boiling point more than propanone’s.
(b) Propanone will be collected first because its weaker intermolecular forces give it the higher vapor pressure at every pressure.
(c) Both liquids will distill together because they reach the same boiling point at 0.80atm.
(d) Water will be collected first because hydrogen bonding makes it more volatile under reduced pressure.