Chapter 10, Problem 10.168MP

When a gaseous compound X containing only C, H, and O is burned in ${\text{O}}_{\text{2}}$ , 1 volume of the unknown gas reacts with 3 volumes of ${\text{O}}_{\text{2}}$ to give 2 volumes of ${\text{CO}}_{\text{2}}$ and 3 volumes of gaseous

${\text{H}}_{\text{2}}\text{O}$ . Assume all volumes are measured at the same temperature and pressure.

(a) Calculate a formula for the unknown gas, and write a balanced equation for the combustion reaction.

(b) Is the formula you calculated an empirical formula or a molecular formula? Explain.

(c) Draw two different possible electron-dot structures for the compound X.

(d) Combustion of 5.000 g of X releases 144.2 kJ heat. Look up $\Delta H{°}_{\text{f}}$ values for ${\text{CO}}_{\text{2}}\left(g\right)$ and ${\text{H}}_{\text{2}}\text{O}\left(g\right)$ in Appendix B, and calculate $\Delta H{°}_{\text{f}}$ for compound X.