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Find more information about Crossref citation counts. The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric. Find more information on the Altmetric Attention Score and how the score is calculated. A new reactive and polarizable molecular model was developed to describe HCl dissociation in liquid water and used to investigate HCl behavior at the air—water interface. It was found that the mechanism of HCl accommodation at the air—water interface began with its hydrogen pointing toward the water as it approached from the air.
This was followed by dissociation into a contact ion pair once solvated at the air—water interface with the hydronium oriented more toward the air than the chloride on average. In comparison with NaCl, HCl showed some similar behavior in that its contact ion pair was stabilized at the air—water interface in comparison with the bulk.
However, dissociated HCl had a greater propensity for the air—water interface than NaCl due to the fact that the hydronium ion was more surface active than sodium. A , , 47 , View Author Information. Louisiana Tech University, P. Box , Ruston, Louisiana , United States.
Cite this: J. A , , 47 , — Article Views Altmetric -. Citations Cited By. This article is cited by 14 publications. Santanu Roy, Gregory K. Schenter, Joseph A. Napoli, Marcel D. Baer, Thomas E. Markland, Christopher J. The Journal of Physical Chemistry B , 27 , The Journal of Physical Chemistry A , 43 , Sobyra , Matthew P.
Melvin , and Gilbert M. The Journal of Physical Chemistry C , 38 , Faust , Thomas B. Because the clusters of type 3-i were fully dissociated at all the level of theories considered in this work, the dissociation of HCl in aqueous solution might expect to take place in a cluster with a maximum of three water molecules.
Once again, as noted above, the dissociation process of HCl was dependent upon the cavity model employed. It is easy to understand this result because the HCl H2O clusters undissociated at all in both the gas phase and aqueous solution. In this work, the geometries of the clusters in aqueous solution were obtained by re-optimizing the gasphase geometries. The optimized geometries are shown in Figure 1 and the energetics on the transferring processes at the MP2 level of theory are summarized in Table 5.
Figure 1. Optimized geometries of the HCl H2O n clusters. At this point, it would be interesting to examine the role of various Gibbs free energies for the dissociation of HCl clusters from the thermodynamic cycle shown in Scheme 1. To distinguish the dissociation phenomena clearly, two different symbols are used to display data in the same table: small and large symbols represent undissociated and dissociated clusters, respectively.
Interestingly, the plot can be divided into four quadrants, I - IV. However, the clusters in IV require large relaxation and solvation free energies because undissociated clusters in the gas phase break down to ionic species in aqueous solution. The clusters belong to III have smaller relaxation but larger solvation free energies because these species dissociate into ionic species even in the gas phase.
Note that there is no data point in II because such a situation is hard to occur. Figure 2. Large and small symbols represent dissociated and undissociated HCl clusters, respectively. Figure 3. Optimized geometries of the HCl H2O 7 clusters. The number of water molecules was limited to seven because the first-solvation shell seems to be completed in the HF H2O 7 cluster see Figure 3.
If the data in Table 6 are displayed in Figure 2, all the points can be found in I and III , which have small relaxation but larger solvation free energies as the number of water molecules increases.
To investigate ionic dissociation process of HF in aqueous solution, a hypothetical dissociation process, Eq. In Eq. Table 6. Table 7. Four different cavity models were examined in aqueous solution. In the case of HCl, the position of water molecule s is an important factor for dissociation, especially water molecule s positioned near to the hydrogen atom. At least three water molecules are required for dissociation. In the case of HF, no dissociation took place until seven water molecules are in close proximity to the weak acid except one case.
From this work, we found that analysis based on thermodynamic cycle can give us unique insight into the dissociation mechanism and the most promising solvation model might be CPCM-MP2 combined with UA0 cavity model in terms of accuracy and reliability of the results. Click here to choose a searching target image or drag and drop a searching target image. Article Info. Introduction The dissociation of an acid in aqueous solution plays a key role in a variety of chemical and biological reactions, and this might be a simple process.
Scheme 2. Table 3. Table 4. Table 5. Note that there is no data point in II because such a situation is hard to occur Figure 2. References Ault, B.
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