Which hydrocarbon will be most stable?

How many chiral compounds are possible on monochlorination of $2$-methylbutane?

Iodination of a hydrocarbon $(C-H \rightarrow C-I)$ with molecular iodine is a slow and reversible reaction. However,it can be carried out in the presence of an oxidizing agent such as

Complete the following reactions:
$(i)$ $n$-heptane $\xrightarrow[773 \ K, 10-20 \ atm]{Cr_2O_3/V_2O_5/Mo_2O_3}$ ?
(ii) $CH_4 + O_2 \xrightarrow[523 \ K, 100 \ atm]{Cu}$ ?

Ethylene dibromide ($1$,$2$-dibromoethane) on heating with metallic sodium in ether solution yields:

Give the mechanism of chlorination of methane.