A Simple 1–1 Electrolyte: Volumetric Properties of Aqueous Solutions of Sulfuric Acid at Elevated Temperatures

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