Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: ananasdoceu on October 10, 2009, 10:35:25 AM
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Hello all,
I am taking IB chemistry, and I have recently done a practical about the reaction between Na2S2O3, and FeCl3.
I used different catalysts such as CaSO4, CuSO4, FeSO4 and NiSO4.
I am sure that many of you are familiar with this experiment, however I am very new to chemistry, and I would like to know exactly what causes the colour change to occur between the first two compounds; why the solution becomes transparent after some time; and how do the other 4 compounds act as catalysts in the reaction?
I would also appreciate some chemical equations to show the reactions which occur.
Many thanks!!!!
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I couldn't find this on Google so I looked in the unutterably tedious and poorly organised "Facts, Patterns and Principles" and found the following
Iron (III) is reduced to Iron(II) via the dark-violet unstable complex anion,[Fe(S2O3)2]-
2Fe3+(aq) + 2S2O32- :rarrow: 2Fe2+(aq) + S4O62-(aq)
Maybe the only item to pull out of that is thiosulphate (in common with its reaction with H+ and I2), acts as a reducing agent - and itself becomes the tetrathionate ion.
I think it is a bit obscure for A-Level/IB to be honest.
I don't know if your question expects this.
Clive