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Recusant
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#1
Report Thread starter 17 years ago
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I'm basing my coursework upon the rates of reaction of the "Iodine clock" experiment reacting Pottasium Iodide with SodiumThiosulphate and Potassium Peroxodisulphate. The Peroxidisulphate ions oxidise the iodide ions to form iodine in aqueous soln. while the thiosulphate ions turn the iodine back into iodide ions, once all the thiosulphate ions are used up, the reaction soln. turns black/blue almost instantaneously as the iodine reacts with the starch (also in the soln. but playing no active part in the reaction). I am still at the planning stage, and no matter how much I research I can't find a suitable catalyst(s) to test and compare, my teacher hinted towards transition metals but I wouldn't know how they act as catalysts or whether I would use a transitional metal by itself as a heterogenous catalyst or perhaps as a complex of some sort in soln. as a homogenous catalyst.
I'm probably missing something really obvious here, and if so I apologise. But any help at all would be much appreciated!
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Kuz
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Report 17 years ago
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(Original post by Recusant)
I'm basing my coursework upon the rates of reaction of the "Iodine clock" experiment reacting Pottasium Iodide with SodiumThiosulphate and Potassium Peroxodisulphate. The Peroxidisulphate ions oxidise the iodide ions to form iodine in aqueous soln. while the thiosulphate ions turn the iodine back into iodide ions, once all the thiosulphate ions are used up, the reaction soln. turns black/blue almost instantaneously as the iodine reacts with the starch (also in the soln. but playing no active part in the reaction). I am still at the planning stage, and no matter how much I research I can't find a suitable catalyst(s) to test and compare, my teacher hinted towards transition metals but I wouldn't know how they act as catalysts or whether I would use a transitional metal by itself as a heterogenous catalyst or perhaps as a complex of some sort in soln. as a homogenous catalyst.
I'm probably missing something really obvious here, and if so I apologise. But any help at all would be much appreciated!
I no this was posted ages ago, but do you still need help, because I'm doing this experiement at the moment for my A2 coursework and I was wondering if we could help each other?

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Haza01299
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#3
Report 16 years ago
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Could do with some urgent help with my peroxodisulphate A2 coursework if anyone could help? Reply please
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amybarwick
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#4
Report 16 years ago
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I've just done my A level coursework on the iodine clock and the catalyst to use is hydrated iron 2 sulphate. It speeds up the reaction really well so you only need a small amount. I used 0.1g and even that was too fast. Good Luck with the experiment!!!
Amyx
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afwaite
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#5
Report 16 years ago
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iron (III) and iron (II) are good catalysts, and transition metals. but iron (II) oxidises to iron (III) readily so iron (III) is probably the easier. it makes no difference to the over all reaction. p.s. im doing my assesed practical tomorrow and have no idea of the method if any one has any tips that would be good
amy x
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