Question 4
Which fraction is separated from the upper part of a crude oil distillation column?
The right answer is the one marked above.
Petroleum gas. It has the lowest boiling point of the fractions, at about −25 °C, so it stays a vapour furthest up the column where the temperature is lowest.
Tar has the highest boiling point and collects at the bottom of the column. Reading that table from top to bottom is reading boiling point from low to high.