The Energy of Dissociation H2O→H+OH

Oldenberg, O.

doi:10.1063/1.1747112

Cited by 10 publications

(11 citation statements)

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“…It is noticeable that the green and orange bands of CaO molecule lie in a similar region as CaOH, which are usually observed in arc-induced plasmas or laser-induced plasmas − of calcium salts in air. The absence (or low abundance) of CaO bands in Figure can be probably due to the fact that, for the dissociation of H 2 O molecules, more energy is required to dissociate H 2 O into H + H + O (218.3 kcal/mol) than into H + OH (118.2 kcal/mol) . It may be thought of in two steps, first producing H + OH and next dissociating OH.…”

Section: Resultsmentioning

confidence: 99%

“…The absence (or low abundance) of CaO bands in Figure 2 can be probably due to the fact that, for the dissociation of H 2 O molecules, more energy is required to dissociate H 2 O into H + H + O (218.3 kcal/mol) than into H + OH (118.2 kcal/mol). 49 It may be thought of in two steps, first producing H + OH and next dissociating OH. Hence, lower population number density of O atoms can be expected in underwater plasmas compared with that of OH radicals.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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CaOH Molecular Emissions in Underwater Laser-Induced Breakdown Spectroscopy: Spatial–Temporal Characteristics and Analytical Performances

et al. 2019

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Recently, molecular emissions from the laser-induced plasma in ambient gas have gained increasing interest; however, very little is known about the case in water solutions. In this work, we investigated the spatiotemporal characteristics of molecular emissions, CaOH for instance, in underwater laser-induced breakdown spectroscopy (LIBS) by using time-resolved spectroscopy, spectral-resolved imaging, and shadowgraph techniques. It was shown that clear CaOH molecular bands can be observed in the spectrum at very early times after the laser pulse and presented a much longer lifetime and more homogeneous emission distribution compared with the Ca I and Ca II lines. Such unique characteristics of CaOH molecular emission inspired us to improve the performances of underwater LIBS by using the CaOH molecular bands instead of Ca I and Ca II lines. We demonstrated the excellent quantification results of CaOH with higher stability, less self-absorption, and reduced matrix effect. Meanwhile, the limit of detection (LOD) of Ca with the CaOH molecular band (2.46 ppm) is comparable to that with the atomic line of Ca I (2.07 ppm), and much lower than that with the ionic line of Ca II (13.81 ppm), indicating a good sensitivity of CaOH. This work gives not only some insights into the molecule formation mechanisms in underwater plasmas, but also provides new ideas to improve the analytical performances of underwater LIBS.

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Section: Resultsmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

CaOH Molecular Emissions in Underwater Laser-Induced Breakdown Spectroscopy: Spatial–Temporal Characteristics and Analytical Performances

et al. 2019

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“…The dissociation of water (H 2 O) molecules into hydrogen (H) and hydroxyl (OH) is one of the most important things in chemical reactions in connection with industrial processes and has been discussed for eight decades. 1 This work was done to provide evidence of experiments to measure the dissociation energy of H 2 O → H + OH that were previously developed photochemically 2 or using the explosion method. 3 Using their own unique method, Lewis and von Elbe predicted the activation energy required to dissociate the water molecule.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Study of an almost Barrier-Free Water Dissociation on a Platinum (111) Surface Alloyed with Ruthenium and Molybdenum

Cahyanto

Zulaehah²,

Widanarto

et al. 2021

ACS Omega

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A theoretical study based on density functional theory for H 2 O dissociation on the metal surface of Pt(111) alloyed simultaneously with Ru and Mo was performed. The determination of the minimum energy path using the climbing image nudged elastic band (CI-NEB) method shows that the dissociation reaction of H 2 O with this catalyst requires almost no energy cost. This dissociation reaction is not only kinetically favored but also almost thermodynamically neutral and somewhat exothermic. The electronic structure analysis showed that much more charge was released in Mo and was used to bind the adsorbed hydroxyl (OH ad ). Further analyses of the density of states (DOS) showed that the large number of orbitals that overlap when OH binds to Mo are responsible for the stabilization of the OH-surface bond. The stability of the OH ad fragment on the surface is believed to be a descriptor for the dissociation of H 2 O with an almost spontaneous process.

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“…The exceptionally low concentration of H 2 O in all tektites is indeed one of the main arguments for the impact origin and could be explained through a mechanism of dissociation of the H 2 O molecules into their atomic components 37 . The H 2 O dissociation into H 2 + ½ O 2 requires a very high energy and, in experimental systems, it is generally obtained from a vapour phase at high temperatures (> > 1000 °C) produced by electric discharge 38 . For comparison with tektites, atomic bomb glasses that form under energetically comparable conditions yield comparable H 2 O concentration in the order of a few ppm 39 .…”

Section: Discussionmentioning

confidence: 99%

3D X-ray tomographic analysis reveals how coesite is preserved in Muong Nong-type tektites

Masotta

Peres

Folco

et al. 2020

Sci Rep

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Muong Nong-type (MN) tektites are a layered type of tektite associated to the Australasian strewn field, the youngest (790 kyr) and largest on Earth. In some MN tektites, coesite is observed in association with relict quartz and silica glass within inclusions surrounded by a froth layer. The formation of coesite-bearing frothy inclusions is here investigated through a 3D textural multiscale analysis of the vesicles contained in a MN tektite sample, combined with compositional and spectroscopic data. The vesicle size distribution testifies to a post-shock decompression that induced melting and extensive vesiculation in the tektite melt. Compared to free vesicles, nucleated homogeneously in the tektite melt, froth vesicles nucleated heterogeneously on relict quartz surfaces at the margins of coesite-bearing inclusions. The rapid detachment of the froth vesicles and prompt reactivation of the nucleation site favoured the packing of vesicles and the formation of the froth structure. Vesicle relaxation time scales suggest that the vesiculation process lasted few seconds. The formation of the froth layer was instrumental for the preservation of coesite, promoting quenching of the inclusion core through the subtraction of heat during froth expansion, thereby physically insulating the inclusion until the final quench of the tektite melt.

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The Energy of Dissociation H2O→H+OH

Abstract: The various lines of evidence regarding the energy of dissociation H2O→H+OH are critically discussed. This gives a basis for discussing the energy of activation of the process OH+OH→H2+O2.

Cited by 10 publications

References 13 publications

CaOH Molecular Emissions in Underwater Laser-Induced Breakdown Spectroscopy: Spatial–Temporal Characteristics and Analytical Performances

CaOH Molecular Emissions in Underwater Laser-Induced Breakdown Spectroscopy: Spatial–Temporal Characteristics and Analytical Performances

Theoretical Study of an almost Barrier-Free Water Dissociation on a Platinum (111) Surface Alloyed with Ruthenium and Molybdenum

3D X-ray tomographic analysis reveals how coesite is preserved in Muong Nong-type tektites

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