Isooctane combustion energy

FigureS.IO Comparison oftemperature profiles along the reactor length axis as calculated for a microchannel steam reformer with integrated catalytic burner for isooctane combustion (case A) and a microchannel steam reformer supplied with energy from hot combustion gases fed into heating channels (case B) [383] S/C ratio was 3.0 in both cases the air excess was 20% in case A and 94% in case B.

The energy required to overcome the barrier to reaction is called the activation energy and is usually given the symbols a or AG. An energy level diagram for a reaction such as the combustion of isooctane is shown below. 

Energy changes in the metabolism of glucose and the combustion of isooctane, a high octane component of gasoline (Opener, Section 6.4)... 

Using tables of thermodynamic data, it is possible to work out the energy differences for many different reactions at different temperatures. For example, for the combustion of isooctane, AC (at 298 K) = -1000kJmorf... 

Since isooctane can exist in an atmosphere of oxygen despite the fact that the equilibrium position really would be completely on the side of the combustion products, the only conclusion we can draw must be that a mixture of isooctane and oxygen cannot be at equilibrium. A small burst of energy is needed to reach equilibrium in a car engine, the spark plug provides this energy and combustion occurs. Without this burst of energy, the petrol is stable and no combustion occurs (as you wUl ruefully be aware if you have ever tried to start a car with a flat battery). 

Kinetically stable means that although the mixture could convert to a more stable set of products, it doesn t do so because an energy barrier separates it from those products. An energy level diagram for a reaction such as the combustion of isooctane is shown below. The products are more stable (lower in energy) than the reactants, but to become the products, the reactants have to overcome a barrier to reaction. This barrier is called the activation energy and is usually given the symbol or AG. ... 

How much energy in kilocalories is emitted by the complete combustion of 386 g of isooctane (CjHij) (Note = -36 kJ/g CgHig.)... 

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