Question

Are `H_3O^+` or `H^+` actual species?

Answer 1

Well it can represent one.....

Explanation:

When an acid dissolves in a solvent it is conceived to increase the concentration of the CHARACTERISTIC CATION solvent of the solvent. And we commonly use water as a solvent....and so should we dissolve `HX` in water, protonolysis of the solvent is conceived to occur......to give the hydronium ion.

`HX(g) +H_2O(l) rarr underbrace(H_3O^+)_"hydronium ion" + X^-`

or more simply we designate the acid principle as `"protium ion":`

`HX(g) stackrel(H_2O)rarr underbrace(H^+)_"protium ion" + X^-`

And note that this is a conception rather than an actuality, the actual acid species, is probably `H_9O_4^+`; a cluster of 3-4 water molecules WITH an EXTRA PROTON, that passes rapidly, tunnels if you like from cluster to cluster. We use `H_3O^+` or `H^+` interchangeably to represent this species in solution.

`HX(g) +H_2O(l) rightleftharpoons underbrace(H_3O^+)_"hydronium ion" + X^-`

The strength of the acid is defined by the completeness of the equilibrium. For strong mineral acids, `H_2SO_4`, `HClO_4`, `HX`, `(X!=F)`, the equilibrium LIES to the right as we face the page.

For weaker acids, `HOAc`, `HF`, `NH_4^+`, the equilibrium lies to the left as written.....