We are asked to determine the fuel value of acetylene.

2 C_{2}H_{2} + 5 O_{2} → 4 CO_{2} +2 H_{2}O

$\overline{){\mathbf{\u2206}\mathbf{H}\mathbf{\xb0}}_{{\mathbf{rxn}}}{\mathbf{=}}{\mathbf{}}{\mathbf{\u2206}}{\mathbf{H}}{{\mathbf{\xb0}}}_{\mathbf{f}\mathbf{,}\mathbf{}\mathbf{products}}{\mathbf{}}{\mathbf{-}}{\mathbf{}}{\mathbf{\u2206}}{\mathbf{H}}{{\mathbf{\xb0}}}_{\mathbf{f}\mathbf{,}\mathbf{reactants}}{\mathbf{}}}\phantom{\rule{0ex}{0ex}}{\mathbf{\u2206}\mathbf{H}\mathbf{\xb0}}_{{\mathbf{rxn}}}\mathbf{=}\mathbf{}[4\u2206H{\xb0}_{f,{\mathrm{CO}}_{2}}+2\u2206H{\xb0}_{f,{H}_{2}O}]\mathbf{}\mathbf{-}\mathbf{}[2\u2206H{\xb0}_{f,{C}_{2}{O}_{2}}+5\u2206H{\xb0}_{f,{O}_{2}}]\phantom{\rule{0ex}{0ex}}{\mathbf{\u2206}\mathbf{H}\mathbf{\xb0}}_{\mathbf{rxn}}\mathbf{=}\mathbf{}\mathbf{[}\mathbf{4}(-395.5\mathrm{kJ})\mathbf{}\mathbf{+}\mathbf{2}(-285.83\mathrm{kJ})\mathbf{]}\mathbf{}\mathbf{-}\mathbf{}\mathbf{[}\mathbf{2}(226.7\mathrm{kJ})\mathbf{+}\mathbf{5}(0\mathrm{kJ})\mathbf{]}\phantom{\rule{0ex}{0ex}}{\mathbf{\u2206}\mathbf{H}\mathbf{\xb0}}_{\mathbf{rxn}}\mathbf{=}\mathbf{}\mathbf{-}\mathbf{2607}\mathbf{.}\mathbf{06}\mathbf{}\mathit{k}\mathit{J}$

The hydrocarbons acetylene (C_{2} H_{2} ) and benzene (C_{6} H_{6} ) have the same empirical formula. Benzene is an "aromatic" hydrocarbon, one that is unusually stable because of its structure.

Determine the fuel value in kJ/g for acetylene.

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