Acids and Bases


According to this theory, acids are proton (H+) donors and bases are proton acceptors.

    HCl + H2O H3O+ + Cl

HCl donates a proton and H2O accepts it. So HCl is acid and H2O is base.

Bare proton (i.e., H+ only) does exist in H2O. It is associated with water molecules i.e., is solvated,


H+ + xH2O



Solvated proton is simply denoted as H3O+, which is called ‘Hydronium ion”. However, hydration number of a proton may be 1, 2, 3, 4 etc., which may be represented as H3O+, H5O2+, H9O4+ etc.

Conjugate acid-base pair

When a substance donates a proton it is converted to a base, the conjugate ...

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