Combustion between hydrogen and oxygen

To explain the kinetic behaviour of such systems Semenov [19,20] and Hinshelwood and Thompson [21,22] have proposed the concept of branching chains. When a pair of ordinary propagation steps occurs, there is no change in the number of chain carriers. When a branching chain occurs, however, there is an increase in the number of carriers. Let us consider the pair of reactions  

In both cases, two chain carriers have been formed from one. When the two reactions are added together the net resnlt is 

Increase in the number of reactive species in the branching chain reaction between H atoms and 

Number of cycles Number of H atoms reacting Number of H atoms produced Number of HjO formed 

in the first cycle of reactions, one H atom produces 3H atoms together with two molecules of water. The numbers produced in subsequent cycles are shown in Table 12.4. After 50 cycles the number of H radicals and water molecules is of the order of the Avogadro constant. The reactions are very fast, and 50 cycles can occur in a fraction of a second. 

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