Question

Hydronium ions are always in the form H₃ O⁺

Answer 1

The strength of an acid is measured in terms of the extent of the dissociation of acid in an aqueous solution. The higher H⁺ ion concentration the stronger is the acid.

H⁺ ion does not exist alone H⁺ ion is being unstable, When an acids dissolve in water. The H⁺ ion from acid always goes to the nearest water molecule to form hydronium ion.
HCl(aq)+H₂O(aq)→H₃O⁺(aq)+Cl-(aq)

H₂O + H⁺  → H₃O⁺ ion