Methane and ethane both can be prepared in one step by which of the following compounds?

$n$-Butane on monochlorination under photochemical conditions gives an optically active compound "$P$". "$P$" on further chlorination gives dichloro compounds. The number of dichloro compounds obtained (ignore stereoisomers) is:

For which of the following are only two isomeric monochloro derivatives possible?

The relative reactivity of $1^o H$,$2^o H$,and $3^o H$ in bromination reaction has been found to be $1 : 82 : 1600$ respectively. In the reaction $CH_3-CH(CH_3)-CH_3 \text{ (excess)} + Br_2$ $\xrightarrow{hv} CH_3-C(Br)(CH_3)-CH_3 \text{ (A)} + CH_3-CH(CH_3)-CH_2-Br \text{ (B)}$,the percentage yields of the products $(A)$ and $(B)$ are expected to be:

$n$-butane on heating with a catalytic mixture of $AlCl_3$ and $HCl$ gives:

Identify the straight-chain hydrocarbon that is an isomer of $3-$ethyl$-2-$methylhexane.