The enthalpy change in the combustion of the hydrocarbon octane is delta H = -5.48 x 10^3 kJ/mol C8H18(l). How much heat, in kilojoules, is liberated per gallon of octane burned? (Density of octane = 0.703 g/mL; 1 gal = 3.785 L.)

Answered below.

162000 kJ

-128000

To calculate the amount of heat liberated per gallon of octane burned, we need to convert the given enthalpy change from kJ/mol to kJ/gal.

1. Begin by converting the density of octane from g/mL to g/L:
- Density of octane = 0.703 g/mL
- 1 gal = 3.785 L
- Therefore, the density of octane = 0.703 g/mL x 3.785 L/gal = 2.657 g/L

2. Next, we need to calculate the molar mass of octane (C8H18):
- Molar mass of C = 12.01 g/mol
- Molar mass of H = 1.01 g/mol
- Molar mass of octane (C8H18) = (8 x 12.01 g/mol) + (18 x 1.01 g/mol) = 114.23 g/mol

3. Now, we can calculate the amount of heat liberated per gallon using the given enthalpy change (delta H) and the molar mass of octane:
- delta H = -5.48 x 10^3 kJ/mol C8H18(l)
- Convert delta H from kJ/mol to kJ/gal by dividing by the molar mass of octane:
delta H per gallon = (-5.48 x 10^3 kJ/mol C8H18(l)) / (114.23 g/mol) = -48.0 kJ/gal

Therefore, the amount of heat liberated per gallon of octane burned is -48.0 kJ/gal. The negative sign indicates that heat is being released during the combustion process.