The halogen which is most reactive in the free radical halogenation of alkanes under sunlight is

Select the chain propagation steps in the free-radical chlorination of methane.
$(1) \, Cl_2 \to 2Cl^{\bullet}$
$(2) \, Cl^{\bullet} + CH_4 \to CH_3Cl + H^{\bullet}$
$(3) \, Cl^{\bullet} + CH_4 \to CH_3^{\bullet} + HCl$
$(4) \, H^{\bullet} + Cl_2 \to HCl + Cl^{\bullet}$
$(5) \, CH_3^{\bullet} + Cl_2 \to CH_3Cl + Cl^{\bullet}$

The reaction of methane with concentrated $HNO_3$ at high temperature yields .........

Explain the difference in the boiling points of the branched structures of pentane $(C_5H_{12})$. Explain how branching affects the boiling point of isomeric alkanes.

Identify the correct statements from the following:
$(i)$ Petrol and $CNG$ operated automobiles cause less pollution.
$(ii)$ Alkanes having tertiary hydrogen can be oxidised to alcohols by $KMnO_4$.
$(iii)$ Methane can be prepared by Kolbe's electrolytic method.
$(iv)$ Alkyl chloride on reduction with zinc and dilute hydrochloric acid gives alkane.

Write the structural formulas of the following compounds:
$(i)$ $3,4,4,5-$Tetramethylheptane
$(ii)$ $2,5-$Dimethylhexane