[Letters]

The order of anion stability is correct for which of the following series?

i) -OCl > -OClO > -OClO2 > -OClO3
ii) [H2SbO4]- > [H2AsO4]- > [H2PO4]-
iii) H3CCOO- < BrH2CCOO- < Br2HCCOO- < Br3CCOO-

That is the question that i have been given, for the first one i know it is not correct because a quick search on wikipedia showed me that -OClO3 was more stable then -OCl, however for the other two i have no idea i cant find them anywhere. Can somebody please either show me a way of recognizing stability or direct me to a source that will help me with this question. Thanks alot

[Letters]

the second on is all the same except for using Sb, As, P and as we go down the periodic table electronegative forces increase which means it will be easier to donate electrons which means that the order: [H2SbO4]- > [H2AsO4]- > [H2PO4]- should also be incorrect when ordered in anion stability. If anyone can confirm or deny this if i am correct it would mean that the third one remains and the question in my book also has the option of none so i will have to find out that one too.

[MrOHBrown]

How about the various electron pairs provided by adding O atoms to the complex? I'd assume that this would provide a sort of "cushion" whereby a negative charge would be stabilised. That'd make me say that 1 is incorrect.

I'd also assume that extra Br would have the same effect, so for this reason I would say 3 is correct.

Another thing to consider is that Sb really is much more stable as a free atom than P would be, and so would form less stable anion than P, Using this reasoning i'd have to say that 2 is incorrect.

Please correct me if I am wrong...

[Letters]

To me that sounds correct and i understand your reasoning, however i am no expert so it would be nice if someone could also confirm or deny. By the way thanks MrOHBrown for responding

[sjb]

The order of anion stability is correct for which of the following series?

i) -OCl > -OClO > -OClO2 > -OClO3
ii) [H2SbO4]- > [H2AsO4]- > [H2PO4]-
iii) H3CCOO- < BrH2CCOO- < Br2HCCOO- < Br3CCOO-

That is the question that i have been given, for the first one i know it is not correct because a quick search on wikipedia showed me that -OClO3 was more stable then -OCl, however for the other two i have no idea i cant find them anywhere. Can somebody please either show me a way of recognizing stability or direct me to a source that will help me with this question. Thanks alot

I'd actually suggest that you have the arrows the wrong way around in part i), as the negative charge is more effectively delocalised around the 4 oxygen atoms (in ClO₄^-) compared to ClO^-

As to part iii) the electron withdrawing effects of the electronegative bromine means that the tribromoacetate is more stable than the triprotioacetate as you have indicated

[MrOHBrown]

No, I think his/her arrows are the right way around, making 3 the correct answer...

However I appreciate you reminding me of terms such as "electron withdrawing effects" - I really should use thos eterms more in class =)

[sjb]

Somewhere along the line I think we're actually agreed

I misread the original question as saying "this is the order", prove me right or wrong.

S