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Old Sep 3rd 2017, 05:53 AM   #1
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Lightbulb Calculating potential of a solution


I'm having some trouble with the following problem:

Calculate the potential of a solution made by mixing equal volumes of 0.20M thallium(I)nitrate and 0.20M dibromine in 1M HCl. E'(Tl3+/Tl+) = 0.77V en E'(Br2(aq)/2Br-) = 1.087V

The answer given is 0.934V

This is what I have so far:

TlNO3 ---> Tl+ + NO3-
Tl3+ + 2e- <---> Tl+
Br2(aq) + 2e- <---> 2Br-

Tl+ + Br2 <---> Tl3+ + 2Br-

The potentials that are given have this 'prime' above them so those are formal potentials (potentials when in certain conditions --> in 1M HCl)

Ecell = E(cathode) - E(anode)

cathode is reduction(Br2 to 2Br-) and anode is oxidation(Tl+ to Tl3+)

I feel like I should use the Nernst equation to calculate E(cathode) and E(anode) but I don't have the concentration of Tl3+ nor do I have the concentration of Br-

How should I proceed, did I miss something?

All feedback is welcome!

(The question was originally in Dutch, this is my best attempt to a translation. How I use subscripts and superscripts so I can make my formulas more nice looking?)
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nernst equation, redox reaction

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