Equilibrium constants of hydrogen–deuterium–tritium self-exchange reactions in water vapor as studied with a pulsed molecular-beam quadrupole mass filter

Abstract

We measured the equilibrium constants KHDO = P2HDO/PH2O⋅PD2O, KHTO = P2HTO/PH2O⋅PT2O, and KDTO = P2DTO/PD2O⋅PT2O at 295.6°K (22.4°C), assuming the mass spectrometric sensitivities of the three species cancel in each expression of the equilibrium constant. The results obtained were KHDO = 3.82±0.05, KHTO = 3.66±0.06, and KDTO = 3.99±0.07. These values agreed with the current theoretical values of KHDO = 3.84, KHTO = 3.69, and KDTO = 3.97 at the same temperature. We discuss the discrepancy of the present value of KHDO as compared with previous experimental determinations, and we conclude that a direct measurement of the mass spectrometric sensitivity ratio for KHDO is still necessary to resolve the disagreement. We prepared the water mixtures that contained tritium by reacting the appropriate hydrogenic gases with oxygen over a platinum sponge catalyst.

On the proper use of the Bigeleisen–Mayer equation and corrections to it in the calculation of isotopic fractionation equilibrium constants

“…For the water vapor internal equilibrium reaction: H 2 O + D 2 O = 2HDO, large deviations were found between theoretical studies and experiments (Pyper et al, 1967;Pyper and Newbury, 1970;Pyper and Christensen, 1975). Wolfsberg (1969) showed that it was not sufficiently accurate to add anharmonic corrections without the contributions of G 0 terms to partition function ratios.…”

“…Table 5 The comparison of equilibrium constant K calculated from this study and those from Wolfsberg et al (1970), Bron et al (1973), Richet et al (1977) and experiments. Wolfsberg et al (1970) and Bron et al (1973) Richet et al (1977 This study Experiments Friedman and Shiner(1966); (b) Pyper and Christensen (1975); (c) Pyper and Newbury (1970); (d) Richet et al (1977); (e) Bron et al (1973).…”

Isotope Effects on the17O,1H Coupling Constant and the17O–{1H} Nuclear Overhauser Effect in Water

“…This shows that a 1% error in the molar fraction leads to an error of about 5% in the equilibrium constant when m 10 and m 30 are near 1:1. (13)) but they refer to reactions in the liquid phase. (14) which is 3.95 Ϯ 0.12.…”

“…The equilibrium constant for this reaction has been measured many times for the gaseous phase (see, for example, (13,14)) but data for solutions are scarce. Gold and Tomlinson (14) measured the equilibrium constant by using 1 H NMR spectra similar to those given in Ref.…”

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“…In recent years, Pyper et al [6] measured the equilibrium constants of Hydrogen-H 2 O isotopic exchange reaction; Benedict et al [7] measured the microwave spectrum and rotational constants for the ground state of D 2 O.…”