Which prefix indicates a molecule with 2 carbon atoms?

Prefix used for a molecule with two carbon atoms is (Eth-).

Explanation:

Those organic compounds which contain two carbon atoms are specified by using a prefix (Eth-).

Examples:

An Alcohol with two carbon atoms = Ethanol

An Alkyne with two carbon atoms = Ethyne

An Alkene with two carbon atoms = Ethene

A Carboxylic Acid with two carbon atoms = Ethanoic Acid

An Aldehyde with two carbon atoms = Ethanall