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cell potential diagram

IMAG2306_1.jpg hi I don't get why on the this question , the diagram would include a pt electrode .
Attachment not found
why is the electrode not cobalt metal ? Is this because in the question , no info is given about the colbalt metal ? Thus a pt electrode is used instead or is it because we have want find the standard cell potential, so a pt electrode is used ?


Thanks
1483535420053-797507610.jpg400.5KB
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Avatar for coconut64
coconut64
OP
16
Also I am a bit confused by the concentration of the co2+ and co3+ ions. It says 1M of both solutions, does it mean there are 2mol dm^-3 of solution in total ? I thought you can only have 1M...
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Avatar for Pigster
Pigster
20
You can't attach a crocodile clip to either Co2+ or Co3+

You are trying to find the voltage when one of the half cells is Co3+ + e- <-> Co2+ NOT Co2+ + 2e- <-> Co or Co3+ + 3e- <-> Co

You have to have the solutions under standard conditions, which is defined as 1 mol dm-3 for each solution. The Co solution must have Co2+ at 1 mol dm-3 AND Co3+ at 1 mol dm-3. That is not 2 mol dm-3.

(actually, as long as both Co2+ and Co3+ are the same conc it would give the same value as both at 1 mol dm-3)

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