Plants use carbon dioxide to make food.
There are two ways to represent the chemical formula of a substance: in condensed form or in structural form. Ethane is an alkane which consist of two carbon atoms. Since the general formula for ethane is CₓH₂ₓ₊₂, the condensed formula is C₂H₆. The structural formula or the line-bond structure is shown in the attached picture.
Because it is an asphyxiant.