[kriggy]

Hi guys,
one of my friends is revising for exams and she asked me: name this compound:
Mg(HAsO₄)₂
I was like haha its easy before I realized that As is in same group as P so its its As⁵⁺ and not As⁶⁺.And the acid is H₃AsO₄
So Im thinking it is just a typo and it should be most likely Mg(HAsO₄) or Mg(H₂AsO₄)₂. Anyway, I just want to make sure I´m not mistaken.
Am I? Or are there any Arsenic shenanigans which I´m not aware of.
Thank you

[Borek]

I would bet on typo. But I don't pretend to know everything about arsenic chemistry.

There is always a slight chance that you are expected to name the compound using systematic approach - IUPAC rules are constructed in such a way it should be possible to name every compound. But I doubt that's the case.

[9-92-6-19]

It could actually be possible; there are some major differences between Phosphorus and Arsenic as oxides. For example, H₃PO₃ is tetrahedral with two O—H bonds that are acidic, one P—H bond, and a P=O; this is quite unlike H3AsO3 which is trigonal pyramidal and acts with three As—OH bonds.
Of course, I'm not a master at Arsenic chemistry, either.