Why is sulfuric acid seen as a strong acid?

Question

Why is sulfuric acid seen as a strong acid?

Answer 1

Sulfuric acid is a strong acid only for the first proton. SulfurOUS acid is the conjugate base of sulfuric acid and it is a weak acid. That second proton come off about as readily as the proton in household vinegar.

Sulfuric acid is H2SO4. The resonance between the oxygen atoms and the resultant delocalized charge makes HSO4- a very stable ion. Stable enough that the dissociation reaction will go towards completion in water, and that's the definitionof a strong acid.

Answer 2

The sulfur atom has a 2+ charge.  The electron density from the -OH oxygen is being pulled toward to the sulfur, which allows the proton to be readily removed.