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Topic: A little confused with the conecpt of electrolytes  (Read 6165 times)

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Offline Eh?

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A little confused with the conecpt of electrolytes
« on: April 28, 2007, 09:47:37 PM »
I understand that when you dissolve salt in water it will form ions, but I don't get why that helps it conduct electricity. I know the positive ion would take in electrons, but what would make it want to give them back up? I also don't really understand what would make a material take in more electrons to give it a negative charge. If the electrons and protons in an atom cancel each other out, then how could more electrons be transfered to it making it negative?

On a side note why does a balloon rubbed on your hair stick to a neutral surface. Sure it is given a surplus of negative charges making it want to attract to a positive charge, but if the wall is neutral then how could it be attracted to it.
« Last Edit: April 28, 2007, 10:06:07 PM by Eh? »

Offline Ch3micat

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Re: A little confused with the conecpt of electrolytes
« Reply #1 on: April 28, 2007, 11:48:03 PM »
I'm not sure I can answer this perfectly, but here is how my teacher explained it to me.

When you have a solid metal, like a sheet of iron, it is essentially alternating sheets of positive and negative, and when a current is going through it, the negative sheet can slide without disturbing the structure of the metal.

Wheras, with a salt, which forms a crystal, its not the same.  When you have a salt, it forms a geometric shape, and you can't move the ions around much without causing the whole crystaline solid from breaking down.  Then, when you put the salt in water, and water grabs each of the ions that compose the salt and seperate them from each other, a current can pass through because it can move between the positive ions without having to disturb the structure like it would with the crystals.   

As far as the hair question, I'm even less of a reference, but most surfaces aren't completely nuetral.   Water for example, has strong hydrogen bonding due to its polarity.  Also, what might be on your hair? Humans contain a lot of water and other crap.

Offline Experte

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Re: A little confused with the conecpt of electrolytes
« Reply #2 on: April 29, 2007, 07:40:02 PM »
Ok what you know now is that a salt, when it is dissolved in water or other polar liquids, dissotiates in its positively and negatively charged ions. However this is not ( at least not alone ) the reason for a current to flow.
the process being actually responsible for the current flow is called electrolysis. You may know of electrolysis concerning the funktion of a battery, what happens in the solution of a salt is in principal the very same.

If you impress a voltage on, for example, a sodium-chloride solution, you will get a site with electron surplus (cathode)  and a site with electron deficiency (anode) . Logically the cation (Na+) is attracted to the site with electron surplus and graps there an electron. In the meantime the chloride ion gives off an electron to the anode, consequently the circuit is closed.

during the current flow Na+ is reduced to elemental sodium and Cl- is oxidized to chlorine gas ( industrially chlorine gas and sodium hydroxide are produced in this way). Naturally, this does not occur without consuming energy and the solution can only conduct electricity well until all NaCl within was converted completely, then the electrical resistance increases dramatically. Now you can also find out what happens if you enhance you voltage ( hint: water contains a slight amount of OH- and H3O+ ions )
I hope my english is easily understandable
       
   

Offline Eh?

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Re: A little confused with the conecpt of electrolytes
« Reply #3 on: April 29, 2007, 07:45:48 PM »
Thanks for your help. It has helped clear some things up. I never considered that the structure would affect it any.

As for the balloon thing I was just using the hair as an example. There was this website I was reading that explained what causes static electricity. I was understanding it until they came to the A balloon negatively charged will stick to a neutral wall.

Offline Borek

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Re: A little confused with the conecpt of electrolytes
« Reply #4 on: April 30, 2007, 03:21:50 AM »
Look at the problem this way - you need freely moving charged particles or molecules to conduct electricity. In metals this role is played by electrons, that can freely move around. In solid ionic salts there is nothing that can move, as all electrons have their fixed positions around ions - so they don't conduct. In pure water there are no charged molecules - so it is an insulator. When you add ionic salt it will dissociate creating charged, freely moving ions - and its conductivity will rise.
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Offline Eh?

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Re: A little confused with the conecpt of electrolytes
« Reply #5 on: April 30, 2007, 08:57:08 PM »
Now that I understand a little better about electrolytes I have another question along the same line. Would it be possible to use something like a capacitor to electrolyze water into breaking into hydrogen and oxygen. For example the positive end would attract the electrons and cause oxidation. If it is possible does anyone know how much voltage would be need to get a positive pull strong enough to pull the electrons apart?

Offline Borek

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Re: A little confused with the conecpt of electrolytes
« Reply #6 on: May 01, 2007, 03:38:55 AM »
Just Google electrolysis. No idea why do you ask for capacitor. DC source (be it battery or power pack) is what you need. Voltage depends on the reaction, you may find standard potentials tables on the web.
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Offline Eh?

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Re: A little confused with the conecpt of electrolytes
« Reply #7 on: May 01, 2007, 04:04:05 PM »
I wasn't talking about the conventional means of electrolyzing water. I hope i can explain this accurately. I mean what would happen if I charged a capacitor and used the electrostatic field to take electrons from water?
here is another way of phrasing the question.
For example say you had a very high voltage/very low ampere generator, and you had earth grounded the negative electrode and had the positive electrode where you can move it around.

Furthermore, the positive electrode is covered with a thin layer of glass, so while it has a very high positive voltage, electrons have a hard time passing thru the glass covering.

If I stick the highly positive electrode into a glass beaker of water, can I ionize the water  with the affects of the voltage field alone?

Offline Borek

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Re: A little confused with the conecpt of electrolytes
« Reply #8 on: May 01, 2007, 04:53:42 PM »
No charge transfer no electrolysis. Some ionisation in extremally strong field seems possible, some ordering of dipoles is more then sure even in not so strong fields.
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