Final answer:
Butene is likely to have a higher molar entropy than cyclobutane because it has a less compact and more extended structure, allowing for a greater number of microstates and more molecular disorder.
Step-by-step explanation:
When comparing the molar entropy of butene and cyclobutane, we should consider the number of available microstates and the molecular complexity of the substances. Entropy, which is a measure of disorder in a system, tends to be higher in substances with more complex molecular structures and more degrees of freedom for their atoms and molecules to move. Butene, which is a linear alkene with the formula C4H8, would be expected to have a higher molar entropy than cyclobutane, which has a cyclic structure. The cyclic structure of cyclobutane makes it more compact and potentially less disordered compared to the more extended structure of butene.
Referring to the concept that substances with similar molecular masses but different structures can have different entropies, n-butane, which is structurally similar to butene, has stronger intermolecular interactions when compared to its isomer 2-methylpropane due to its larger surface area. Though this information pertains to boiling points, it reflects the more extended structure of n-butane, similarly to butene, and informs us that larger surface areas and more extended structures in molecules like butene could contribute to a higher entropy compared to more compact molecules like cyclobutane.