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Topic: Reaction for light-sensitive potassiumtris(oxalato)ferrate(III)  (Read 7764 times)

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Offline Fmeub

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I know that the crystal surfaces of potassiumtris(oxalato)ferrate(III) will turn yellow if they are not stored in the dark, but how do I explain it by using reaction equations?

I suppose the light gives energy in the form hv, but I'm not sure whether any bonds break.

Offline resc

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Re: Reaction for light-sensitive potassiumtris(oxalato)ferrate(III)
« Reply #1 on: May 27, 2008, 02:24:21 PM »

The photosensitive nature of this compound is used in actinometry (look up ferrioxalate actinometry). Light reduces the Fe3+ to Fe2+ and the oxalate form CO2:

2Fe3+ + C2O42- (hv) --> 2Fe2+ + 2CO2

You can then add something like 1,10-phenanthroline if you want to quantify the Fe2+ and hence the amount of photons, by measuring the absorption of the iron-phenanthroline complex.

So in answer to your question, bonds do break as the complex goes via an excited state, and one of the pathways deactivating this excited state is decomposition.

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