AP Chemistryhardmcq1 pt
Which fuel releases the most energy per gram when burned?
A.H₂ (ΔH_comb = −286 kJ/mol)
B.CH₄ (−890 kJ/mol)
C.C₈H₁₈ (−5471 kJ/mol)
D.C₂H₅OH (−1367 kJ/mol)
Explanation
Core Concept
Per gram: 286 kJ ÷ 2.02 g = 142 kJ/g — far above methane (55.6), octane (48), or ethanol (29.7). Hydrogen's tiny molar mass concentrates energy.
Correct Answer
AH₂ (ΔH_comb = −286 kJ/mol)
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