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Well, the K+ ions aren't accepting the electrons. The Cu2+ ions are. They are then forming Cu(s) on the cation. The opposite is happening on the other side of the voltaic cell. The Zn(s) is being oxidized and releasing electrons and this makes more Zn2+ ions in solution. The salt bridge is there because if it wasn't a build up of charge would accumulate at opposite ends reversing the flow of current, so the ions slowly move to there respective sides. This is caused by the potential difference (ie Voltage). Eventually there is less and less Zn(s) to release electrons due to the diminishing anion. And the current stops flowing. Also when the current stops flowing the change in charge at each end stops changing and then ions don't move etc. This is why the battery "runs down". It uses up all the anion through the chemical process. And there is nothing left to donate electrons via the circuit.
Lockdown, your explanation is how my chemistry textbook explains it as well. I may be wrong, but according to what I've learned about electricity, there would be no current without the salt bridge. If the electrons aren't flowing through the salt bridge, then there by definition can be no current, as the current must flow in a continuous loop, including within the source. So it's the difference between the chemistry and the current explanations that's confusing me. Thanks!
When you connect just an anion and cation in solution to each other without a salt bridge, there will be a momentary current (maybe a second or so tops) this is due to the fact that the Cu2+ ions attract the electrons slightly more than the Zn(s) can hold onto them. However, the moment this happens, the electrons will flow, but due to a lack of positive ions in the salt bridge(there being none) a separation of charge will occur (as positive charge builds up at the Anion, and negative charge at the cation). This will apply a potential difference (and as such an electric field and thus a force) that is stronger than the force of the Cu2+ ions to attract and maintain the electrons and as such the current will stop and reverse itself back to equilibrium.
Also, Electrons do not flow in the salt bridge they flow through the circuit. Positive ions and negative ions are flowing in the salt bridge. So the negative charge build up is canceled by the addition of K+ ions, and the positive charge build up is canceled by the SO4- ions. The electrons aren't free moving, ions are.
Lockdown, by "when you connect an anion and cation in solution to each other without a salt bridge...", did you mean "when you connect an anode and a cathode in solution to each other without a salt bridge"? One of the requirements for current to flow is that there must be a COMPLETE closed loop. So, while there is voltage even without the salt bridge, there is no current. If you would put a bulb in that circuit, I'm not sure it would light up even for half a millisecond. The explanation with the sulfate ions (-) moving into the anode and the potassium ions (+) moving into the cathode makes sense to me. However, it doesn't square away with the way that the current must be transferred through the salt bridge in order for the loop to be complete. Someone please help.
yes sorry, haha. Anode and Cathode. The reason there is a slight(and I mean slight) flow (which is negligible, you wont notice anything) is because in the instant that the anode and cathode are connected there is a slight attraction from the cathode (Cu(s)) on the electrons in the Anode(Zn(s)), but the moment the electrons try to transfer, the charge discrepancy creates a field and reverses the transfer, and this force is stronger than the attractive force of the cathode. There is technically no current due to the almost instantaneous reverse. But there is still for an instant or so, a movement of charge. One reason you may be confused is because you are assuming that current is just electron flow. While in most metals the flow of charge is due to moving electrons, in a solution the current is actually the flow of charge caused by the ions in solution, not free electrons. That might be one reason you are confused. In normal circuits electrons flow through conductors(slowly I might add), but in many fluids and plasma the charges are ions in solution or molten substances.
Lockdown, I think I got it. Thanks so much for your help!
no problem, glad I could