Chapter 18, Problem 114AP

Many hydrocarbons exist as structural isomers, which are compounds that have the same molecular formula but different structures. For example, both butane and isobutane have the same molecular formula of ${\text{C}}_{\text{4}}{\text{H}}_{\text{10}}$. Calculate the mole percent of these molecules in an equilibrium mixture at $\text{25°C}$, given that the standard free energy of formation of butane is -15.9 kJ/mol and that of isobutane is -18.0 kJ/mol. Does your result support the notion that straight-chain hydrocarbons (i.e., hydrocarbons in which the C atoms are joined along a line) are less stable than branch-chain hydrocarbons?