Hydrocarbons standard molar entropies

Predict which of the hydrocarbons below has the greater standard molar entropy at 25°C. Explain your reasoning. 

Molar entropies increase as the size and complexity of the molecule increases. Compare, for example, the standard molar entropies of the three two-carbon hydrocarbons ... 

Point 4 is related to the molecular motion discussed in Section 19.3. In general, the number of degrees of freedom for a molecule increases with increasing number of atoms, and thus the number of possible microstates also increases. Figure 19.13 compares the standard molar entropies of three hydrocarbons in the gas phase. Notice how the entropy increases as the number of atoms in the molecule increases. 

A FIGURE 13-7 Standard molar entropies of some hydrocarbons... 

Table 2.1 Change in standard molar Gibbs energy, enthalpy and entropy (all in kj mot ) for the transfer of hydrocarbons from pure liquids into water at 25 °C (Prausnitz, Lichtenthaler and de Azevedo, 1999 Gill and Wadso, 1976). Notice the large negative entropy changes due to the hydrophobic effect, in the case of n-butane, the entropy decrease amounts to 85% of the Gibbs energy of solubilization, while for other hydrocarbons the entropic contribution is even larger...

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