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Non Life Sciences => Chemistry => Topic started by: Chemistry4me on 21/02/2009 06:01:09

Title: What is the blue solution?
Post by: Chemistry4me on 21/02/2009 06:01:09

When ammonium vanadate (NH₄VO₃) is dissolved in dilute sulfuric acid and the solution is treated with an excess of sulphur dioxide, a blue solution is formed...
What is the blue solution? I have searched high and low and still can't find a definitive answer... [>:(][>:(]

Title: What is the blue solution?
Post by: lightarrow on 21/02/2009 08:22:17

Quote from: Chemistry4me on 21/02/2009 06:01:09

When ammonium vanadate (NH₄VO₃) is dissolved in dilute sulfuric acid and the solution is treated with an excess of sulphur dioxide, a blue solution is formed...
What is the blue solution? I have searched high and low and still can't find a definitive answer... [>:(][>:(]

SO₂ in acidic solution reduces VO₃^- (n.o. of vanadium = +5) to VO²⁺ (n.o. of vanadium = +4) which is blue.

Title: What is the blue solution?
Post by: Chemistry4me on 21/02/2009 11:33:00

Thanks lightarrow [:)]
I was wondering if it was VO²⁺
It appears that it is.

Title: What is the blue solution?
Post by: Chemistry4me on 22/02/2009 01:53:10

You know what the SO₂ is oxidised to? SO₃^2-? SO₄^2-?

Title: What is the blue solution?
Post by: lightarrow on 22/02/2009 11:55:19

Quote from: Chemistry4me on 22/02/2009 01:53:10

You know what the SO₂ is oxidised to? SO₃^2-? SO₄^2-?

The last you have said. It's the only possibility, think about it. Which is the n.o. of S in SO₂ and in SO₃^2-? It's the same.  [:)]
So S is oxidized to +6, which means SO₄^2- in water solution (or HSO₄^- in strong acidic solution).

By the way, the reaction from vanadate and SO₂ is exploited industrially to make H₂SO₄; vanadium +4 is then re-oxidized by air to vanadium +5 and so it acts as catalyzer.

Title: What is the blue solution?
Post by: Chemistry4me on 23/02/2009 02:51:22

Thank you [:)] again.
Haha, obviously I was NOT thinking!