JEE Main 8 Jan 2020 Shift 1 Solved Paper

When the difference between the B.P. of the two liquids is less than around 40°C, fractional distillation is more efficient.
The difference between the boiling points of isohexane and 3-methylpentane is only 3 degrees.
So, fractional distillation is the best suitable method. Since, isohexane has a lower boiling point, it comes out first.