Porous Disk

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Nicole Gamboa 2M
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Porous Disk

Postby Nicole Gamboa 2M » Sun Feb 05, 2017 1:52 pm

Hi All,
I know that we didn't talk about this much in class so it probably won't be too important, but I was wondering what the difference was between a porous disk and a salt bridge, as well as why we use salt bridges instead of porous disks when calculating the potential of a cell.

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Re: Porous Disk

Postby Chem_Mod » Sun Feb 05, 2017 2:04 pm

The porous disk was just another way of accomplishing the same function as the salt bridge. For the design we see, in galvanic cells, we need the salt bridge because the solutions are separate, and we need a way for ions to flow between the two. For another design, like Daniel cells, or the electric pile were the porous disk was used, the electrodes are in the same solution, and the porous disk would allow for movement of ions in the solution (6ed Figure 14.3 for a Daniel cell). The porous disk method is not as accurate when measuring cell potential, since there is an intermixing between the two redox species.

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Re: Porous Disk

Postby Jenny_Thompson_3I » Sun Feb 05, 2017 2:07 pm

A salt bridge is when you have two different solutions that are in different beakers while a porous disc is used in a concentration cell in which you have two solutions that are the same but are at different molarities. Also, a porous disc is used when there is only one beaker while a salt bridge is for two beakers.

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