Brønsted acids. The hydrogen ion H+ never exists on its own in a condensed phase, as it is always solvated to a certain extent. The high negative value of H0 in SbF5/HSO3F mixtures indicates that the solvation of the hydrogen ion is much weaker in this solvent system than in water.
Brønsted acids are defined as species that never exist independently in a condensed phase, but rather are always partially surrounded by solvent molecules. The high negative value of H0 in SbF5/HSO3F mixtures implies that the solvation of the hydrogen ion is weaker in this solvent system compared to water.