Some automobiles and buses have been equipped to burn propane \(\left(\mathrm{C}_{3} \mathrm{H}_{8}\right) .\) Compare the amounts of energy that can be obtained per gram of \(\mathrm{C}_{3} \mathrm{H}_{8}(g)\) and per gram of gasoline, assuming that gasoline is pure octane, $\mathrm{C}_{8} \mathrm{H}_{18}(l) .\( See Example \)6.11 .$ ) Look up the boiling point of propane. What disadvantages are there to using propane instead of gasoline as a fuel?

For this step, we'll write the balanced combustion reactions for both propane and octane. Combustion reactions involve reacting with oxygen to produce carbon dioxide and water. For propane: C3H8(g) + 5O2(g) -> 3CO2(g) + 4H2O(l) For octane: C8H18(l) + 12.5O2(g) -> 8CO2(g) + 9H2O(l)

To compare the amounts of energy produced per gram of propane and octane, we'll need their enthalpy of combustion values. The enthalpy of combustion for propane is \(-\,2220.0\, kJ/mol\), and for octane, it is \(-\,5471.0\, kJ/mol\). The molar mass of propane is \(44.10\, g/mol\) and that for octane is \(114.22\, g/mol\). Now, we will calculate the amount of energy produced per gram by dividing the enthalpy of combustion by the molar mass. For propane: Energy per gram = \(\frac{-2220.0\, kJ/mol}{44.10\, g/mol} = -50.34\, kJ/g\) For octane: Energy per gram = \(\frac{-5471.0\, kJ/mol}{114.22\, g/mol} = -47.88\, kJ/g\)

From the calculations in step 2, we can compare the energy produced per gram of propane and octane: Propane: \(-50.34\, kJ/g\) Octane: \(-47.88\, kJ/g\) Propane produces around \(2.46\, kJ/g\) more energy than octane per gram.

The boiling point of propane is \(-42^\circ C\).

Some disadvantages of using propane as a fuel instead of gasoline are: 1. Due to its lower boiling point, propane must be stored in pressurized tanks, which leads to increased weight and more complex fuel systems. 2. Propane has lower energy density than gasoline, which means that vehicles running on propane will need larger fuel tanks and have a lower range before refueling compared to vehicles running on gasoline. 3. The infrastructure for propane fueling stations is not as widespread as gasoline, making it difficult to find refueling options, especially in remote areas. 4. Propane handling and maintenance require special training, and potential safety hazards to the vehicle owner and the mechanic increase. In conclusion, while propane can produce more energy per gram compared to gasoline, the disadvantages of using propane as a fuel are the low boiling point, complex storage system, lower energy density, and less developed infrastructure.