Synthesis of Hydrogen Bromide by Free-Radical Chain Reaction

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This Demonstration considers the gas phase reaction of hydrogen with bromine to produce HBr. The overall reaction is:



Plots are shown of the concentrations of all five species involved in the reaction. The reaction proceeds through a free-radical chain mechanism. Initiation is the production of bromine atoms through photochemical excitation. Propagation of the chain repeatedly produces hydrogen atoms and hydrogen bromide molecules. Termination of the chain occurs when hydrogen and bromine atoms combine.


Contributed by: Edward Li and Akash Mukherjee (June 2017)
Open content licensed under CC BY-NC-SA



The experimental rate law can be determined from the differential equations of the initiation, propagation, inhibition and termination steps, as given in the Initialization code.

Special thanks to the University of Illinois NetMath program and the Mathematics Department at William Fremd High School.


[1] W. R. Salzman. "Chain Reactions." (Jun 9, 2017)

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