TBR: Salt Bride Clarification

[justadream]

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TBR GC page 292 #47

TBR says this statement is true:

“Anions flow through the salt bridge from the cathode to the anode”



I get that anions flow to the anode and cations flow to the cathode. But are those anions “from the cathode”???



Aren’t the anions/cations that leave the salt bridge coming from the SALTS in the bridge (not from the anode/cathode half-cells)?



If so, I guess TBR just said “from the cathode to the anode” as a way to indicate direction (not that the ions are actually going from the anode/cathode half-cell to the salt bridge to the other anode/cathode half-cell ).

 

[Chrisz]

Th Think about that. When we first have a cell that is not connected to wires. we have equal moles cations and anions in each container, so the net charge in each container is simply zero. After connecting the wire, cations are produced by oxidizing metal on the anode side, and metal is produced by reducing the cations on the cathode side. On the anode side, we will have + charge, and on the cathode side, we will have - charge. You right, salt bridge works by releasing anions on the anode side and cations on the cathode side to balance the charge.

 

[justadream]

@Chrisz

Yes, I understand that anions need to go to the anode and cations need to go to the cathode.

I was wondering where those anions and cations are really from (as in, from the salt bridge)?

So technically, isn't it possible that the salt bridge at some point runs out of ions to provide?

 

[Chrisz]

@justadream, as clearly stated in my explanation salt bridge releases cations and anions. Some salt bridge containes KNO3 and some salt bridge contains Na2SO4.