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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: arctic-cube on June 04, 2009, 01:46:40 PM

Title: Anion Analysis
Post by: arctic-cube on June 04, 2009, 01:46:40 PM

Hi there,

There's a solution, which may contain one or more of the following ions: B^-, I^-, S₂O₃^2-, SO₃^2-, SO₄^2-, S^2-.

1. If I add sulphuric acid the solution gets brown, a brown-like gas is being released (at least I think, maybe it's just the glas getting brown on the inside) and after a short while there's a black sediment.

2. By adding a lot of AgNO₃(aq) there's a yellow sediment and some black sediment, too.

- What do you think is inside the solution by taking all the ions in account.
- What do you think is inside, if S^2- and S₂O₃^2- are excluded, do some of the results still make sense? Especially the black sediment in part 2, does any one of these beside S₂O₃^2- make such thing? The problem is that I didn't see a change from orange to brown to black, neither by waiting some time.

So far I'm pretty sure that S^2- is not included, same with B^- (what's the brown stuff from?)