Thermodynamics of hydrogen-isotope-exchange reactions. 4. Determination of K and. delta. S/sup 0/ for the reaction D/sub 2/(g) + H/sub 2/O(l) in equilibrium H/sub 2/(g) + D/sub 2/O(l)

Journal Article · Thu Mar 10 00:00:00 EST 1988 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100316a059· OSTI ID:7247112

Zhang, R; Rock, P A

This paper reports their results for the direct experimental determination of the equilibrium constant and its temperature dependence for the hydrogen-isotope-exchange reaction D/sub 2/(g) + H/sub 2/O(l) in equilibrium H/sub 2/(g) + D/sub 2/O(l). The reaction was studied in an electrochemical double cell without liquid junction of the type Pt(s)/D/sub 2/(g)/NaOD(daq,m)/HgO(s)/Hg(l)/HgO(s)/NaOH(aq,m)/H/sub 2/(g)/Pt(s), where (daq,m) denotes a D/sub 2/O solution. The experimental value of the equilibrium constant at 25.0/sup 0/C for the reaction is K = 12.30 +/- 0.09; the experimental value of ..delta..S/sup 0/ at 25.0/sup 0/C for the reaction is -8.1 +/- 1.7 J x K/sup -1/. The experimental results are compared with theoretical calculations within the framework of the Born-Oppenheimer approximation. The comparison suggests a failure of the Born-Oppenheimer approximation of about 4% in the value of the calculated equilibrium constant for the reaction. When Kleinman and Wolfsberg's corrections for the failure of the Born-Oppenheimer approximation are taken into account, the experimental result for the equilibrium constant is in excellent agreement with the calculated value.

• Research Organization: Univ. of California, Davis (USA)
• OSTI ID: 7247112
• Journal Information: J. Phys. Chem.; (United States), Vol. 92:5
• Country of Publication: United States
• Language: English

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