Question

How to write the name of Hau3+ ion using stock notation. For example HAuCl4 is written as.......(lll) chroride. Fill the blank space?

Answer 1

See explanation

Explanation:

To explain this better I'll use reversible reactions.

You think that:
`"HAuCl"_(4(aq)) rightleftharpoons "HAu"_((aq))^(3+)+4"Cl"_((aq))^(-)`

Instead, it is:
`"HAuCl"_(4(aq)) rightleftharpoons "H"_((aq))^(+)+"AuCl"_(4(aq))^(-)`

`"HAuCl"_(4(aq))` is an acid (chloroauric acid), so the hydrogen ion dissociates from the rest of the molecule. A clearer explanation is brought on with the diagram for the acid structure:

So, there is no `"HAu"_((aq))^(3+)` ion, but there is a `"AuCl"_(4(aq))^(-)` ion, called tetrachloroaurate:

By the way, the only compound I know fitting the name of _(III) chloride, is Gold(III) chloride (`"Au"_2"Cl"_6`)