Answer:
Option a) C2H6, ethane, has the lowest boiling point.
Step-by-step explanation:
Ethane (C2H6) has the lowest boiling point among the given options because it has the smallest molecular size and the weakest intermolecular forces compared to the other alkanes listed.
Boiling point is primarily determined by the strength of intermolecular forces. In alkanes, the main intermolecular force is London dispersion forces, which arise due to temporary fluctuations in electron distribution. Larger molecules generally have more electrons and thus experience stronger dispersion forces.
In this case, ethane (C2H6) has the smallest molecular size and the lowest number of electrons among the options. This results in relatively weaker dispersion forces between ethane molecules compared to the larger alkanes. As a result, less energy is required to break these weaker forces, leading to a lower boiling point for ethane compared to the other alkanes in the list.