Question

What must an Arrhenius acid contain?

Answer 1

An Arrhenius acid is a substance whose aqueous solutions give rise to hydrogen ions or protons.

Explanation:

And thus we may identify as an acid a species that undergoes the following reaction with water...

`HX stackrel(H_2O)rarrH^+ + X^-`

The acidium ion, `H^+`, is an hypothetical species, and is more commonly represented as hydronium ion, i.e. `H_3O^+`, i.e.

`HX(aq) + H_2O(l) rarrH_3O^+ + X^-`

Both `H^+`, and `H_3O^+` are labels of convenience (the latter is more common these days. The actual acidium ion is PROBABLY a cluster of 3-4 water molecules with an EXTRA proton, `H^+`...to give `H_7O_3^(+)` or `H_9O_4^(+)`. The proton is presumed to tunnel from cluster to cluster, we write `H_3O^+` without loss of generality.

And so an Arrhenius acid must contain an hydrogen ion that can be transferred to solvent....