Is H2SO4 a Broensted acid

Multi-protonic acids

Table 1 contains acids such as hydrochloric acid (HCl), but also acids such as sulfuric acid (H2SO4) and phosphoric acid (H3PO4). These acids differ in the number of bound H atoms and thus in the number of protons that they can release in a protolysis. The hydrochloric acid is one monoproton Acid. Sulfuric acid is one biprotonous and phosphoric acid one three-proton Acid. In the case of multi-protonic acids, the protons are always released gradually. This means that for every proton released we have one Dissociation stage can write down. This is shown in Figure 5 using the example of sulfuric acid.

Figure 5: Dissociation stages of the biprotonic acid H2SO4 (sulfuric acid)

One proton is given off by the acid for each dissociation stage. In the 1st stage of dissociation arise from sulfuric acid (H.2SO4) in water (H2O) hydrogen sulfate (HSO4-) and an oxonium ion (H.3O+). Since every dissociation stage represents a chemical equilibrium, the ions formed are converted back into the substances used in the reverse reaction. The following conjugated acid-base pairs can be named for this dissociation stage: H2SO4/ HSO4- and H3O+/H2O.

The hydrogen sulfate (HSO4-) can either act as a base in the reverse reaction or as an acid in the 2nd stage of dissociation react. The hydrogen sulfate carries a proton, which can also be given off. We consider again the dissociation in water (H.2O). Another oxonium ion (H.3O+) and a sulfate ion (SO42-). The following conjugated acid-base pairs can be named for this dissociation stage: HSO4-/SO42- and H3O+/H2O.

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Note:Multi-protonic acids have more than one proton bound in their structure. A dissociation stage can be written down for each proton, with each dissociation stage representing an equilibrium reaction.