Final answer:
To find the fuel value of C5H12 (pentane), divide the heat of combustion, -3535 kJ/mol, by the molar mass of the compound, which is approximately 72.15 g/mol, to get a fuel value of approximately -49.0 kJ/g.
Step-by-step explanation:
To calculate the fuel value of C5H12, given that ΔH°comb is -3535 kJ/mol, we use the energy content of the fuel per mole, which is the heat of combustion. The fuel value is commonly given in energy per mass, such as kJ/g. First, we need the molar mass of C5H12. This is calculated by summing the atomic masses of carbon and hydrogen in the molecule (5 carbons at approximately 12.01 g/mol each and 12 hydrogens at approximately 1.008 g/mol each).
Once we have the total molar mass of C5H12, we divide the heat of combustion by the molar mass to get the fuel value in kJ/g:
Molar mass of C5H12 = (5 × 12.01 g/mol) + (12 × 1.008 g/mol) = 72.15 g/mol
Fuel value (kJ/g) = Heat of combustion (ΔH°comb) / Molar mass of C5H12
Fuel value (kJ/g) = -3535 kJ/mol / 72.15 g/mol
Fuel value (kJ/g) ~= -49.0 kJ/g