University of Oulu

Vielma, T., Hnedkovsky, L., & Hefter, G. (2021). A Simple 1–1 Electrolyte: Volumetric Properties of Aqueous Solutions of Sulfuric Acid at Elevated Temperatures. Journal of Chemical & Engineering Data, 66(8), 3219–3225.

A simple 1–1 electrolyte : volumetric properties of aqueous solutions of sulfuric acid at elevated temperatures

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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, Western Australia 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: American Chemical Society, 2021
Publish Date: 2021-08-13


Densities of aqueous solutions of sulfuric acid (H₂SO₄) have been measured by vibrating tube densimetry at molalities m varying from 0.02 to 3.0 mol·kg⁻¹, at temperatures over the range 323.15 ≤ T/K ≤ 523.15 at 10 MPa pressure. These results were used to calculate the corresponding apparent molar volumes Vϕ(H₂SO₄,aq) and appear to be the first-ever systematic study of the volumetric properties of this important acid at elevated temperatures. At T ≤ 373.15 K, the present results aligned well with recent literature data and with values reported in the 1926 International Critical Tables. No reliable experimental data were found for comparison at higher temperatures. The present results confirm that at lower concentrations and temperatures, sulfuric acid solutions exist as a variable mixture of H⁺(aq) + HSO₄⁻(aq) + SO₄²⁻(aq). However, at higher temperatures, the degree of association increases markedly such that at T ≥ 448.15 K, sulfuric acid solutions behave like a simple 1:1 electrolyte [H⁺(aq) + HSO₄⁻(aq)] even at low concentrations. The variation of Vϕ(H₂SO₄,aq) over the entire experimental region was well modelled using a simple Pitzer equation that specifically included (where appropriate) the effects of chemical speciation. Combination of this model with relevant literature data enabled estimation of the standard ionic volume V°(HSO₄⁻,aq) and the standard volume change ΔrV° for the reaction H+(aq) + SO₄²⁻(aq) → HSO₄⁻(aq) at temperatures up to 523 K.

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Series: Journal of chemical & engineering data
ISSN: 0021-9568
ISSN-E: 1520-5134
ISSN-L: 0021-9568
Volume: 66
Issue: 8
Pages: 3219 - 3225
DOI: 10.1021/acs.jced.1c00291
Type of Publication: A1 Journal article – refereed
Field of Science: 116 Chemical sciences
Funding: This work was funded by the Finnish Cultural Foundation (T.V.) and Murdoch University. The research visit of T.V. to Murdoch University was funded by the Walter Ahlström Foundation (Finland).
Copyright information: © 2021 The Authors. Published by American Chemical Society. CC BY 4.0.