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Topic: Electrophresis  (Read 5325 times)

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hvalarcon

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Electrophresis
« on: April 15, 2005, 01:16:33 PM »
I think that the topic is called electrophoresis, but anyways might as well explain my question to you. My professore introduced a pair of electrode (cathode and anode) into a NaCl solution contained in a beaker. Because this is an aqueous environment you get the dissasociation of the ions and you have Na and cl ions hydrates in soultion right? Then when you get to introduce the two electrodes and introduce an electric current and a voltage enough to make Na+ and Cl- ione attract to the respective electrodes. First of all the ions are hydrated so they aren't supposed to be attracted to toher ions because water isolates the ion from these kind of interactions, am i right? Well first of all how do you get cl- and Na+ ions going to the electrodes. My second and most important question is related to some concept i have about electric circuits. For current to flow through a circuit it needs to be closed, right? so if you introduce both electrode into the solution you don't close the circuit unless you have an electrolite there. Nonetheless, i saw on class the reaction Na+ + 1E-=Na and also 2cl-=cl2 + 2e-
why is this so important for the transport of electron form one cathode to the other. In other words what is happening chemically to transport the chemicals from the cathode to the anode.

Offline Borek

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Re:Electrophresis
« Reply #1 on: April 15, 2005, 06:24:23 PM »
Quote
In other words what is happening chemically to transport the chemicals from the cathode to the anode.

Diffusion. Whether diffusion is a chemical process is a philosophical question :)

Na+ and Cl- ions move thanks to the diffusion. They are hydrated but it doesn't mean they lost charge. However, electrical forces (working on ions in electrical field between electrodes) can be neglected when compared with diffusional processes. To close the circuit you need charge transfer on the elcetrodes - here chemical reactions take place.

Electrophoresis is something different - you use much higher voltage to move particles in the strong electric field.
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TCUrob

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Re:Electrophresis
« Reply #2 on: April 18, 2005, 07:40:50 PM »
My second and most important question is related to some concept i have about electric circuits. For current to flow through a circuit it needs to be closed, right? so if you introduce both electrode into the solution you don't close the circuit unless you have an electrolite there.

Correct, but remember you DO have an electrolyte there. An electrolyte is a molecule that ionizes when dissolved or in a molten state. Here, your Na+ and Cl- atoms are ions. They act as your electrolytes. Water can do the same thing.

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