M/J 2014/P12/Q5
Crude oil is fractionally distilled in a fractionating column. The positions at which fractions X and Y are collected from the fractionating column are shown.
Which statement is correct?
A The temperature increases up the column.
B X condenses at a lower temperature than Y.
C X has a higher boiling point than Y.
D X has longer chain molecules than Y.
Answer: B
Explaination
In fractional distillation, those hydrocarbons (few carbon atoms) which have low boiling points are condensed and collected at the top of the fractionating column. The bigger hydrocarbons are collected at the lower sections of the column.
Hence, fraction X is lighter or smaller with low boiling point (small chain HC) than Y (which is heavier with bigger chain HC) with higher boiling point that’s why fraction X condensed and collected at the top of the column having low temperature.
