Identify the molecular formula of an alkane that exhibits only two different structural isomers.

$A$ fuel has the same knocking property as a mixture of $70\%$ isooctane and $30\%$ $n$-heptane. The octane number of the fuel is .............

The number of chain isomers possible for the hydrocarbon with molecular formula $C_5H_{12}$ 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

Isomers of hexane,based on their branching,can be divided into three distinct classes as shown in the figure. The correct order of their boiling point is

Total number of isomeric compounds (including stereoisomers) formed by monochlorination of $2$-methylbutane is................