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

Briefly explain the trends in boiling point and melting point in the alkane series.

Which of the following formulas represents a saturated cyclic compound?

When $sec$-butylcyclohexane reacts with bromine in the presence of sunlight,the major product is:

In Wurtz reaction,alkyl halides react with:

The compound $(X)$ on $(i)$ heating in the presence of anhydrous $AlCl_3$ and $HCl$ gas gives $2,4$-dimethylpentane,$(ii)$ aromatization gives toluene,and $(iii)$ cyclisation gives methylcyclohexane. The correct name of compound $(X)$ is: