Gasoline is composed primarily of hydrocarbons, including many with eight carbon atoms, called octanes. One of the cleanest-burning octanes is a compound called $2,3,4-$ trimethylpentane, which has the following structural formula:

$$\begin{array}{c}{\mathrm{CH}_{3} \mathrm{CH}_{3} \mathrm{CH}_{3}} \\ {\mathrm{H}_{3} \mathrm{C}-\mathrm{CH}-\mathrm{CH}-\mathrm{CH}-\mathrm{CH}_{3}}\end{array}$$

The complete combustion of one mole of this com-

pound to $\mathrm{CO}_{2}(g)$ and $\mathrm{H}_{2} \mathrm{O}(g)$ leads to $\Delta H^{\circ}=-5064.9 \mathrm{kJ}$ (a) Write a balanced equation for the combustion of 1 mol of $\mathrm{C}_{8} \mathrm{H}_{18}(l) .$ (b) By using the information in this problem and data in Table $5.3,$ calculate $\Delta H_{f}^{\circ}$ for $2,3,4$ -trimethylpentane.