Porous Disk

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Ray Guo 4C
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Joined: Fri Sep 28, 2018 12:15 am

Porous Disk

Postby Ray Guo 4C » Fri Feb 22, 2019 10:47 pm

I have two questions about porous disks.

1. When a porous disk is used, why do electrons flow through electrodes instead of through the solution to the other half-cell?

2. When a porous disk is used, are the reactants mixed? If they are, why don't they react directly without donating electrons to and receiving from electrodes?

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Joined: Fri Sep 28, 2018 12:26 am

Re: Porous Disk

Postby armintaheri » Sat Feb 23, 2019 4:47 am

1. Because the ions in solution are not exchanging electrons. The solid electrodes are exchanging electrons. And the only way for them to do that is to send electrons through the wire. The ions that are dissolved in solution have already been oxidized/reduced, and do not participate in any more reactions.

2. I believe the solutions do mix a little bit since they are in contact, but the disk prevents them from completely mixing together. But even if some mixing does happen, it doesn't cause a problem. This is because when atoms from the anode donate electrons to the cathode, that side of the cell becomes more negatively charged, and the anode side becomes more positively charged. The ions in the cathode solution are positively charged themselves, so they would be repelled by the increasingly positive anode solution and would have no reason to cross over. The dissolved ions from the anode would be attracted to the increasingly negative cathode solution, but even if they do cross the disk to the other side it won't matter because they have already donated their electrons and can no longer react.

Note: This stuff gives me a headache so it would be nice if someone else could confirm that everything I just said makes sense and I didn't get confused somewhere

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