Energy Calculations

carbon-atom-6-largeTHERMODYNAMICS is a subject that makes smart men quail and lesser men run to the nearest exit.
However, we live in a world increasingly dominated by energy use and creation, so that I have invented a simpler calculation not requiring more than a page to explain.

The energy of any fuel or Cc-Hh-Oo compound (where c, h and o are the numbers in the compound formula) can be calculated using the following rules and exceptions:

Carbon, C= 420kJ/mole
Hydrogen= 120 kJ/mole
Oxygen = – 90 kJ/ mole (minus, since it represents a partial combustion).

These numbers will predict the heat of combustion of all “normal” C-H-O compounds with better than 15% accuracy! And that is about the limit to which many of them are known.

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EXAMPLES: Methane, CH4, = 420 + 4(120) = 900 kJ/ mole. (889) Methanol CH4O = 420 + 4(120) – 180 = 720 kJ/mole (726) (The numbers in () are the official vales.).

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EXCEPTIONS

The above applies to all “normal” CHO compounds and fuels.
It does NOT apply to compounds like acetylene, (super unstable) or carbon monoxide or hydrogen gas, H2, which I call “extra energetic (“hyperenthalpic”). They are actually 280 kJ/mole, rather than the 240 predicted by the above rules.

It does NOT apply to CO2 and H2O.

SUPER stable compounds. They would predict the heat of combustion as 60 kJ/ mole, but they are the “Zero” energy of our chosen scale. I call them “hypoenthalpic”.

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