Which of the following carbon count classification is accurate for gases?

The classification of gases based on carbon atom count typically refers to lighter hydrocarbons that exist in gaseous form at standard temperature and pressure. Gases such as methane (1 carbon atom), ethane (2 carbon atoms), propane (3 carbon atoms), and butane (4 carbon atoms) fit into the category of having less than 5 carbon atoms. These hydrocarbons are predominantly found in natural gas and are characterized by their low molecular weight, which allows them to remain in a gaseous state under standard conditions.

In contrast, hydrocarbons that contain between 6 and 15 carbon atoms typically form liquids, such as various types of gasoline and kerosene. These molecules possess higher boiling points due to their larger size and increased molecular weight. Similarly, substances with more than 20 carbon atoms usually consist of heavier oils and waxes, which are solid or viscous at standard conditions.

Having exactly 4 carbon atoms, while it does pertain to a gaseous compound (butane), does not encompass the broader classification of all gases, making it less accurate as a broad criterion compared to the category of having less than 5 carbon atoms. Thus, the most accurate classification for gases is one that indicates they contain less than 5 carbon atoms