15. The Rates of Chemical Reactions   Previous PageNext Page
       The Hydrogen-Iodine Reaction

An example of a long-standing error in reaction mechanisms, which we and others have used so often because it apparently is so well-behaved. The reaction is


and the observed rate equation is

For nearly seventy-five years, everyone assumed that the process occurred by the collision of one hydrogen molecule and one iodine molecule, with enough energy to bring about reaction.

Only as recently as 1967 was it demonstrated that the actual reaction involves the reversible dissociation of I2 molecules into atoms, followed by the reaction of these I atoms with H2 :


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