Compare the parts I highlighted in red - not all of your compounds are consistent with the oxidation/hydration sequence.
So are you saying HCl, HI, HNO3, and HBr don't "match". Is this because there isn't 4 oxygens attached to it? If something is exhaustively oxidised with oxygen, can it turn oxygen into O + 2e- O2- instead of bonding with it?
Let's take HI as an example. The acid
) is produced by exhaustive oxidation of an element.
What is the oxidation state of I in HI?
What is the oxidation state of I in elemental I2
Can oxidation of I2
You also suggested perchloric acid as an option for
). Does this fit with the reactions A
This question is not so crazy if you consider the information generally.
is liquid - so A must be a non metal, and probably not a very heavy one.
A can exist in multiple oxidation states, some of which are even (you are told +2). An even oxidation state strongly suggests an even group number. Now we have narrowed it down to only a handful of elements.
We know the highest oxide is strongly acidic in water, this limits the options even further, and at this point you can write out the formulae of the possible oxoacids E, look at the possible stoichiometries of the reaction with NaOH and solve for the atomic weight of A.
Alternatively, with very little chemical knowledge, you can probably assume
) is either mono-, di- or triprotic. Write the 3 general equations for the reactions with NaOH, and solve for the atomic weight in each case and pick the one that makes sense.
) is monoprotic:
H + NaOH
18 mmol NaOH means: 18 mmol AOx
H means: 18 mmol A (which weighs 290 mg) means: atomic weight of A is 16 g/mol.
Is that a sensible answer? If not, move on and calculate for diprotic... etc. until you reach a sensible answer.Edit: Lettering mistakes corrected