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# An application of the iodine-thiosulphate titration- pos. rep for whoever helps me watch

1. Theory

the first high temperature superconductors were a group of oxides of yttrium, barium and copper formula YBA2Cu30x. The value of x depends on the oxidation state of the copper. To determine the oxidation state of the copper (and hence x), the copper from the superconductor is reacted with iodide ions. The copper is reduced to Cu 1+ and the iodide is oxidised to iodine. The iodide thus produced is titrated against sodium thiosulphate. n.b. Yttrium normally exists as a 3+ ion. Neither Yttrium nor barium reac with the iodide ions.

Practical

0.0100 moles of the superconductorwere used. The copper in it was reacted with excess iodide ions. The iodine produced was made upto 100cm cubed in a volumetric flask, and 10cm cubed portions were extracted with a pipette and titrated against 0.500 mol/dmcubed sodium thiosulphate. Concordant readngs of 8.00cmcubed were obtained.

Question

Calculate the oxidation state/s of the copper in the superconductor and hence the value of x.
2. Hehe, I think I know which school you go to!

And If Im right you really should be doing that question yourself...

Just write out the balanced equations of all of he reactions that occur and you should be able to work it out from there. Sorry I cant be of more help, it wouldnt really be fair
3. oh ****!!! who are u and wer do u go to school?
4. ok anyone else?
5. (Original post by chazzinio)
ok anyone else?
Here are the steps you need to follow. Which one(s) do you have problems with? I won't give you the answer but I am happy to help you get there!

EDIT: I have edited the below having actually tried the question! 1-4 are simple calculations. 5 requires some thought but once you have it, 6 is fairly simple algebra and 7 is simple!

1) how many moles of sodium thiosulphate are in the titre volume
2) how many moles of iodine reacted with this thiosulphate
3) how many moles of iodine were in the original volumetric flask

4) how many moles of copper were present in the amount of wire used

5) Think about the equations for Cu2+, Cu3+ and Cu4+ being reduced to Cu+ then write a general equation for Cuy+ being reduced
6) combine the info from 3) 4) and 5) to get the charge on the copper ion (y+)
7) what was the oxidation state of the copper using 6) and the info in the question
6. I got x=6.6 which may be incorrect.
7. Ok, i think it may be YBa2Cu3O8. anyone agree?
8. I go to NS, as I presume you do. To give you my name would be telling.
9. (Original post by Apprentice)
I go to NS, as I presume you do. To give you my name would be telling.
haha!! you werent very helpful. Ive done it now anyway.
10. It is YBa2Cu3O7

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Updated: April 15, 2006
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