The tetraethyl lead mixed in petrol works as

An alkane (molecular weight $72$) forms only one monochlorinated product. Its formula is

Pick out the alkane which differs from the other members of the group.

What are $X$ and $Y$ respectively in the following reaction sequence?
Isopentane $\xrightarrow{KMnO_4} X$ $\xrightarrow{\text{dehydration}} \underset{\text{Major}}{Y}$

The reaction of $n$-butane with bromine in the presence of light at $725\,^oC$ yields ...................

On treating a mixture of two alkyl halides with sodium metal in dry ether,$2-$methylpropane was obtained. The alkyl halides are