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Where the octane number is raised by blending in ethanol, energy content per volume is reduced. Ethanol energy density can be compared with gasoline in heat-of-combustion tables. It is possible for a fuel to have a Research Octane Number (RON) more than 100, because iso-octane is not the most knock-resistant substance available today.
Note that the especially high molar values, as for paraffin, gasoline, water and ammonia, result from calculating specific heats in terms of moles of molecules. If specific heat is expressed per mole of atoms for these substances, none of the constant-volume values exceed, to any large extent, the theoretical Dulong–Petit limit of 25 J⋅mol ...
The n-octanol-water partition coefficient, K ow is a partition coefficient for the two-phase system consisting of n-octanol and water. [1] K ow is also frequently referred to by the symbol P, especially in the English literature. It is also called n-octanol-water partition ratio. [2] [3] [4]
where H v is the heat of vaporization of water, n H 2 O,out is the number of moles of water vaporized and n fuel,in is the number of moles of fuel combusted. [9] Most applications that burn fuel produce water vapor, which is unused and thus wastes its heat content.
For example, the blood/gas partition coefficient of a general anesthetic measures how easily the anesthetic passes from gas to blood. [5] Partition coefficients can also be defined when one of the phases is solid , for instance, when one phase is a molten metal and the second is a solid metal, [ 6 ] or when both phases are solids. [ 7 ]
Octane rating is measured relative to a mixture of 2,2,4-trimethylpentane (an isomer of octane) and n-heptane. There are different conventions for expressing octane ratings, so the same physical fuel may have several different octane ratings based on the measure used. One of the best known is the research octane number (RON).
Octane is a hydrocarbon and also an alkane with the chemical formula C 8 H 18, and the condensed structural formula CH 3 (CH 2) 6 CH 3. Octane has many structural isomers that differ by the location of branching in the carbon chain .
A closely related property of a substance is the heat capacity per mole of atoms, or atom-molar heat capacity, in which the heat capacity of the sample is divided by the number of moles of atoms instead of moles of molecules. So, for example, the atom-molar heat capacity of water is 1/3 of its molar heat capacity, namely 25.3 J⋅K −1 ⋅mol ...