Identify the final product $C$ in the following reaction sequence:
$Br-(CH_2)_5-Br$ $\xrightarrow{Na, \text{D.E.}} A$ $\xrightarrow{Br_2, \Delta} B$ $\xrightarrow{\text{alc. KOH}, \Delta} C$

$A$ hydrocarbon of molecular mass $72 \ g \ mol^{-1}$ gives a single monochloro derivative and two dichloro derivatives on photochlorination. Give the structure of the hydrocarbon.

At $25,^oC$,Ethylene glycol is a:

$A$ hydrocarbon $C_{5}H_{10}$ does not react with chlorine in the dark but gives a single monochloro compound $C_{5}H_{9}Cl$ in bright sunlight. Identify the hydrocarbon.

What is the difference in molar mass of Undecane and Dodecane?

Arrange the following in increasing order of boiling point.
$(i)$ methane,butane,propane,pentane,ethane.
$(ii)$ $n$-pentane,neo-pentane,iso-pentane.
$(iii)$ ethane,$2$-methyl propane,propane,$n$-butane.
$(iv)$ $2$-methyl pentane,$2,2$-dimethyl butane,$2,2$-dimethyl propane.