Activation-energy for the reaction h+oh--]eaq- - kinetic determination of the enthalpy and entropy of solvation of the hydrated electron

B. Hickle, Knud Sehested

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    The reaction between atomic hydrogen and hydroxide ion in aqueous solutions H + OH- - eaq- + H20 has been studied by pulse radiolysis. The rate constant was measured at pH 11.7 and 12 by following the growth of the hydrated electron absorption at 600 nm. The activation energy of the reaction has been determined over the temperature range 15-60 "C as 6.3 f 0.6 kcal/mol(26.4 f 2.5 kJ/mol). From this value and the activation energy of the reverse reaction, the ea; enthalpy of formation AHf = -32.6 f 1.6 kcal/mol (-136.4 f 6.7 kJ/mol) and its standard entropy So = 16.7 f 5.4 cal/(mol deg) (69.8 f 22.5 J/(mol deg)) were calculated. The high entropy of solvation A& = 11.7 f 5.4 cal/(mol deg) (49 22.6 J/(mol deg)) when electrons are transferred from gas phase into aqueous solution indicates that the hydrated electron is a structure breaker.
    Original languageEnglish
    JournalJournal of Physical Chemistry
    Issue number24
    Pages (from-to)5271-5274
    Publication statusPublished - 1985

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