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

On cracking petrol,we get

The decreasing order of boiling points of the following alkanes is:
$(a)$ Heptane
$(b)$ Butane
$(c)$ $2-$methylbutane
$(d)$ $2-$methylpropane
$(e)$ Hexane
Choose the correct answer from the options given below:

Which of the following compounds is not obtained when a mixture of $CH_3Br$ and $C_2H_5Br$ is treated with sodium metal in the presence of dry ether?

What is the condition to obtain $C_2H_5Cl$ in excess?

Of the $5$ isomeric hexanes,the isomer which can give $2$ monochlorinated compounds is