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Any time combustion is involved in a system, bonds are broken and formed. Since combustion is an overall exothermic process, the energy released when bonds are broken is greater than the energy absorbed when bonds reform to create new products. The overall change in energy is known as a fuel value.

Fuel values are a consideration when building an efficient combustion engine. The table lists certain fuels and their corresponding elemental composition by mass percent.

Using this information, which fuel would give the most amount of energy for a 153 gram sample?

C (mass percent) H (mass percent) Fuel Value (kJ/g)
Charcoal 100 -- 34
Hydrogen -- 100 142
Wood (pine) 50 6
Bituminous coal (PA) 77 5 --
Crude Oil (Texas) 85 12 --
Natural gas 70 23 --

Pine wood.


Coal from Pennsylvania.


Crude oil from Texas.


Natural gas.

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