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### Self Test 6L.2A

Posted: Sun Feb 23, 2020 7:28 pm
Write the diagram for a cell with a hydrogen electrode on the left and an iron(III)/iron(II) electrode on the right. The two electrode compartments are connected by a salt bridge, and platinum is used as the conductor at each electrode.
I am unsure how to approach this problem. Can someone explain step by step how to get the answer?

### Re: Self Test 6L.2A

Posted: Mon Feb 24, 2020 12:17 am
When writing out a diagram, the || means a salt bridge and a | means an interface between phases or a porous disc. The hydrogen cell is on the left, so you'd first write the hydrogen cell portion:
H2 (g) | H+
We use the bar here because both phases are interacting. Because Pt is used as the conductor, you'd add it like this:
Pt | H2 (g) | H+
Next, we write the salt bridge:
Pt | H2 (g) | H+ ||
Now we add the iron portion. We use a comma because they are in the same phase/
Pt | H2 (g) | H+ || Fe3+, Fe2+
Finally, because Pt is the conductor here, add it at end, with the bar
Pt(s) | H2(g) | H+(aq) || Fe3+(aq), Fe2+(aq)| Pt(s)