About a Trillion Times More Acidic than Expected? On the Difference Between the Hammett H₀ and the Unified pH Acidity of Sulfuric Acid.

ABSTRACT: We report on the considerable difference between the distinct pH and Hammett's H₀ acidity function in the entire H₂O-H₂SO₄ mixing range. The Hammett acidity for 100 wt% H₂SO₄ is accepted with H₀ = -11.9. We measured the pH acidity using two different electrochemical cells, operating with at least one hydrogen electrode, giving for 100% sulfuric acid pHabsH2O${\mathrm{pH}}_{{\mathrm{abs}}}^{{{{\mathrm{H}}}_{\mathrm{2}}}{\mathrm{O}}}$ as -24 ± 2. This value was confirmed by high-level compound calculations using the DLPNO-CCSD(T) level at the basis set limit and COSMO-RS solvation. Thus, the difference between both scales amounts to pHabsH2O${\mathrm{pH}}_{{\mathrm{abs}}}^{{{{\mathrm{H}}}_{\mathrm{2}}}{\mathrm{O}}}$

SUBMITTER: Radtke V 

PROVIDER: S-EPMC12723472 | biostudies-literature | 2025 Dec

REPOSITORIES: biostudies-literature