A flask contains a mixture of isohexane and 3-methylpentane. One of the liquids boils at ${60}^{°}C$ while the other boils at ${63}^{°}C$.  What is the best way to separate the two liquids and which one will be distilled out first?

Isohexane and 3-Methylpentane having same molecular formula.

Isohexane boil at ${60}^{°}C$ and 3-Methyl pentane boil at ${63}^{°}C$. Both having low boiling point difference so Fractional distillation is useful for separation and Isohexane having low boiling point so comes out first.