Which functional group having two carbon atoms does not give a compound?

State reasons to explain why covalent compounds:
$(i)$ are bad conductors of electricity?
$(ii)$ have low melting and boiling points?

$CH_{3}COOCH_{3}$ is the molecular formula of which compound?

Unsaturated hydrocarbons contain multiple bonds between two $C$ atoms and show addition reactions. Give the test to distinguish ethane from ethene.

Write the molecular formula of benzene and state the number of double bonds in its structure.

State the meaning of functional group in a carbon compound. Write the functional group present in $(i)$ ethanol and $(ii)$ ethanoic acid and also draw their structures.