Final answer:
The initial boiling point of commercial propane at 14.7 psia is approximately -42.1°C, which is the temperature where its vapor pressure equals atmospheric pressure.
Step-by-step explanation:
The initial boiling point of commercial propane at 14.7 psia is approximately -42.1°C. This value is the temperature at which the vapor pressure of propane equals the external pressure surrounding the liquid, in this case, 14.7 psia, which is equivalent to atmospheric pressure at sea level. The boiling point of a substance can vary with changes in external pressure; hence, propane would boil at different temperatures if the external pressure were to be higher or lower than 14.7 psia.
Boiling points of substances, including propane, can be predicted based on molecular structure and intermolecular forces. Propane, being a nonpolar molecule, experiences London dispersion forces, which are influenced by the molecular mass of the substance. Among the alkanes mentioned, propane has the lowest molecular mass, leading to the lowest boiling point compared to alkanes with higher molecular masses, such as butane and pentane.