$CH_3-CH_2-COO^{-} Na^{+} \xrightarrow[\Delta]{NaOH + ?} CH_3-CH_3 + Na_2CO_3$. Consider the above reaction and identify the missing reagent/chemical.

$CH_4$ is formed when:

Give the name,formula and structure of the cycloalkane which has only one structure.

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:

The general formulas for alkene and alkane are respectively:

The number of shared pairs of electrons in propane is