Identify the reactivity order for halogens towards alkanes.

When ethyl bromide and $n$-propyl bromide are allowed to react with $Na$ metal in dry ether,the number of different alkanes formed is

$5 \, L$ of an alkane requires $25 \, L$ of oxygen for its complete combustion. If all volumes are measured at constant temperature and pressure,the alkane is

$A$ 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.

$A$ sample of gasoline contains $81\%$ iso-octane and $19\%$ $n$-heptane. Its octane number will be

Alkanes are generally resistant to oxidation under mild conditions. What is your opinion regarding the following reaction?
$C_4H_{10(g)} + \frac{13}{2}O_{2(g)} \to 4CO_{2(g)} + 5H_2O_{(l)}$