Two gaseous fuels are considered for a spacecraft thruster

CHEMISTRY · Subjective · A Level · Chemistry · Energetics · Energetics

Problem

Two gaseous fuels are considered for a spacecraft thruster. Fuel 1:

\mathrm{CH_4}

Fuel 2:

\mathrm{C_2H_4}

Combustion reactions (gases throughout): 1.

\mathrm{CH_4 + 2\,O_2 \rightarrow CO_2 + 2\,H_2O}

\mathrm{C_2H_4 + 3\,O_2 \rightarrow 2\,CO_2 + 2\,H_2O}

Average bond energies (

\text{kJ mol}^{-1}

): C–H 413, C=C 614, C–C 348, O=O 498, C=O (in CO

_2

) 799, O–H 463. Which fuel releases more energy per gram upon complete combustion, and what is that approximate energy release (nearest

1\,\text{kJ g}^{-1}