Question

What is the difference in properties between H₃O⁺ & H⁺ ?

Answer 1

H+ ion means the hydrogen ion. it is liberated out of acids, when they are dissolved into water. and the liberation of H+ ions is the cause of the acidic behavior of an acid.

and when this H+ ion gets joined with water molecules, it forms the hydride ion, i.e. H3O+. we can also say that this ion is responsible for acidic behavior of an acid.

hydride ion can also be written as aqueous hydrogen ion, i.e. H3O+(aq.).

thus there is a very slight difference between these two ions, that the former is present already in acids, and the latter is formed upon the reaction of acids with water.