Acids hydrolyze or dissolve in solutions to form Protons.
Acid are defined according to three different theories and concepts.
i) Arrhenius Concept
ii) Lowry Bronsted Theory
iii) Lewis Theory
According to Arrhenius Concept of Acid and Base, "Acid is any specie which when dissolved in water ionizes to produce H⁺ ions".
Example:
HCl → H⁺₍aq₎ + Cl⁻₍aq₎
H₂SO₄ → 2 H⁺₍aq₎ + SO₄²⁻₍aq₎
Proton (H⁺):
Hydrogen atom with atomic mass of 1 amu contains one proton and one electron in its first shell. When this single electron is removed from hydrogen atom it is left with only one proton hence, H⁺ is called proton.
Hydrolysis:
In simple, hydrolysis is that reaction in which water molecules are utilized to breakdown a chemical compound.
Hence, we can conclude that Arrhenius Acids when added to water are being hydrolyzed by water molecule and yield H⁺ (proton) along with corresponding negative specie.