University of Oulu

Tuomas Vielma, Lubomir Hnedkovsky, Glenn Hefter, Chemical speciation effects on the volumetric properties of aqueous sulfuric acid solutions, The Journal of Chemical Thermodynamics, Volume 158, 2021, 106408, ISSN 0021-9614,

Chemical speciation effects on the volumetric properties of aqueous sulfuric acid solutions

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Author: Vielma, Tuomas1; Hnedkovsky, Lubomir2; Hefter, Glenn2
Organizations: 1Research Unit of Sustainable Chemistry, University of Oulu, Oulu 90014, Finland
2Chemistry Department, Murdoch University, Murdoch, WA 6150, Australia
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 0.8 MB)
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Language: English
Published: Elsevier, 2021
Publish Date: 2021-03-30


Densities of fifteen aqueous solutions of sulfuric acid (H₂SO₄) have been measured by vibrating-tube densimetry at solute molalities (m) from (0.01 to 3.0) mol·kg⁻¹ over the temperature range 293.15 ≤ T/K ≤ 343.15. These data have been used to calculate the corresponding apparent molar volumes Vϕ(H₂SO₄,aq), which represent a significant expansion of the volumetric database for this industrially-important acid. At 298.15 K the present results agree well with literature data, notably with the century-old values given in the 1926 International Critical Tables. At other temperatures, where comparisons are possible agreement with the present Vϕ values is also very satisfactory. Consistent with earlier studies, Vϕ(H₂SO₄,aq) was found to exhibit an abnormally-large decrease at low concentrations (m ≤ 0.1 mol·kg⁻¹). This effect is consistent with a change in the chemical speciation of H₂SO₄(aq), from an essentially 1:1 electrolyte (H⁺(aq) + HSO₄− (aq)) at higher concentrations to a predominantly 1:2 electrolyte (2H⁺(aq) + SO₄²⁻ (aq)) in dilute solutions. The Vϕ values were modelled using variants of Young’s rule and the Pitzer formalism. Combination of these results with literature values for the standard volume V°(SO₄²⁻,aq) enabled estimation of V°(HSO₄−,aq) and the standard volume change, ΔrV°, for the first protonation of the sulfate ion (H⁺(aq) + SO₄²⁻(aq) → HSO₄−(aq)) as functions of temperature. It is shown that V°(HSO₄−,aq) is sensitive to the value of the first protonation constant and probably cannot be determined to better than ± 0.3 cm³·mol⁻¹ at present.

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Series: Journal of chemical thermodynamics
ISSN: 0021-9614
ISSN-E: 1096-3626
ISSN-L: 0021-9614
Volume: 158
Article number: 106408
DOI: 10.1016/j.jct.2021.106408
Type of Publication: A1 Journal article – refereed
Field of Science: 116 Chemical sciences
Funding: This work was funded by Walter Ahlström Foundation (TV) and Murdoch University.
Copyright information: © 2021 The Author(s). Published by Elsevier Ltd.This is an open access article under the CC BY license (