[gavindor]

In the case of electrolysis of silver nitrate



there's the silver rod which is an anode and electrons get sucked up from it into the + of the battery. And the silver rod becomes oxidised.

But if we look at a case where instead of a silver rod you have a graphite rod.. / graphite electrode..



(so in this image for the lead bromide, 'cos of the way the battery is oriented, the anode on the right)..

That anode is some inert material like graphite..

But what is going on there.  Electrons are coming out of it yet it doesn't get oxidised. Why and How?!

I get that in the case of Silver electrons leave and it gets oxidised.

And in the case of graphite, graphite doesn't tend to oxidise because each graphite atom has 4 electrons in its outter shell  and it's a small atom , the electrons aren't inclined to be given up.  So  Is it that the electrons that come up the graphite electrode, are electrons not from the graphite, but from and only from, the ions that react at that anode. (the anions that oxidise at it)?

[Hunter2]

No, graphite is a more or less inert material. So there will be no major reaction to it. At anode (+) the Anions in this case Bromide Br- loose there electrons and neutral bromine is developed. The electrons go into the material and travel through the battery  to the cathode (-) . There the positive lead cathions will gain these electrons and lead will be plated.

In the silver case the anode material can be oxidised,  it is not inert, so at anode silver get as Ag+ in solution and left the electron. These travel through the battery to cathode side where silver ions gain it and get plate on the copper Ring.

[gavindor]

Thanks.

Could you clarify with a quote of which part  or parts of what I wrote you are saying no to?

I agree that Graphite is  inert and that no atoms leave the graphite. And that there is no reduction or oxidation of the graphite.

And e.g.

Is this part of what I wrote correct? "So  Is it that the electrons that come up the graphite electrode, are electrons not from the graphite, but from and only from, the ions that react at that anode. (the anions that oxidise at it)?"

(This is in contrast to a silver anode as there electrons are coming from the anode itself)

You write "The electrons go into the material and travel through the battery"

What do you mean by material? Like, what substance are you referring to?

Regarding where you write of electron travel.. and "through the battery"

The electrons go into the material and travel through the battery

 I don't agree that electrons travel through the battery. My research into this has indicated that they don't.  I understand that the battery consists of two separate chambers.. and ions could travel across, if there's a porous wall, but my understanding is that electrons wouldn't.

[Hunter2]

The NO is regarding for the reaction of the graphite.
Here we have an INERT material. The electrons are from the Anions,  but dont harm the graphite, they travel inerside by the electrical current. Graphite is conductiv.
In case of the silver they harm it and corrode it. Ag+ is dissolved into the solution.
The travel of electons through a battery of course is more complicated process. Here I say it to understand it more simple. Instead of a Battery can also use an electronical rectifier.

[gavindor]

The NO is regarding for the reaction of the graphite.
Here we have an INERT material.

Okay but I have always been in total agreement that it's an inert material so you are saying "no" and "NO" to something I didn't say. So that could be a "YES" it's an inert material. And Silver isn't.

You mention "Graphite is conductiv" Well, silver is conductive too.


So I think my question re what is going on with the electrons at a graphite anode (like lead bromide case),  And silver anode (like silver nitrate electroplating case), stands.

It's as if electrons go into and/or leave from, a storage area of an electrode,  in the case of an electrode that doesn't oxidise or reduce.  Like the copper cathode/ring in  silver nitrate, or the graphite anode or graphite cathode in lead bromide.

But what is going on there isn't clear to me.

When the graphite anode receives electrons it doesn't know those electrons came from elsewhere. Yet (it's as if), The electrons get busy with the graphite in some way, but in a way distinct from the electrons that graphite "owns".
(The graphite would be a conductor for electrons it "owns", in the sense of electrons that were with it originally, and electrons that come from elsewhere,.   but there does seem to be some distinction that leads it to not get oxidised/reduced, making it inert. I'm wondering what's going on behind the scenes with this inertness with the conductivity in electrolysis)


 

[Hunter2]

It's because of the electrical potential. The electrons are driven from minus to plus. In solution the ions are kind of boats. So a negative bromide carries one passenger one electron.This leaves this boat and enter the anode material. If the anode material is inert, like graphite, gold, platinum etc. it travels trough this material through the whole circuit to the cathode. If its ignoble, it can react and corrode the anode.
Again if the material is inert the electrons jump into the orbitals of the material and then travel driven by the voltage potential. If the material is ignoble the electrons react and dissolve the material. Ions are produced.

[gavindor]

It's because of the electrical potential. The electrons are driven from minus to plus. In solution the ions are kind of boats. So a negative bromide carries one passenger one electron.This leaves this boat and enter the anode material. If the anode material is inert, like graphite, gold, platinum etc. it travels trough this material through the whole circuit to the cathode. If its ignoble, it can react and corrode the anode.
Again if the material is inert the electrons jump into the orbitals of the material and then travel driven by the voltage potential. If the material is ignoble the electrons react and dissolve the material. Ions are produced.

Well, with the silver anode in the silver nitrate electroplating example, then it seems to me that as soon electrons get sucked up and out of it and into the + terminal of the battery,  the silver anode corrodes/shrinks/gets pits in it. And there's no ion meeting the silver anode, only atoms leaving it as cations, while it oxidises.

I suppose if you had a silver electrode in the lead bromide example, then it might be more like you are describing.. But then in addition to the oxidation going on from electrons getting sucked out the top of it into the + of the battery and Ag+ ions come off the silver rod. You write "In solution the ions are kind of boats. So a negative bromide carries one passenger one electron.This leaves this boat and enter the anode material.".  So you seem to be talking about ions meeting the anode.

That does happen in the case of a graphite anode in the lead bromide example, but I don't think that happens in the case of the silver anode in the silver nitrate example. And i'm not sure that'd happen if a silver anode was used in the lead bromide example.

(As far as I know, currently), it certainly doesn't happen to the silver anode in the silver nitrate example.

Would oxidation ever happen in two ways . (eg if a silver anode was used in the lead bromide example). Those two ways being   A) The silver atoms leave the silver rod as Ag+ cations.  And B)Anions get oxidised at the silver rod.

You seem to mention "B" happening but you don't mention "A" happening.

Thanks

[Hunter2]

Also in the silver case ions involved. The nitrate ions.

Nitrate travels to plus and catch the silver and release one electron into the electrode. On cathode side silver gain the electron and release the nitrate.

[gavindor]

Also in the silver case ions involved. The nitrate ions.

Nitrate travels to plus and catch the silver and release one electron into the electrode. On cathode side silver gain the electron and release the nitrate.

okay thanks

Are there any cases where a silver anode would lose silver while also gaining a coating from some anions that stick onto it?  (Or if not then any case where a metal anode would lose its metal material while also getting coated with some other material).

I know in the silver nitrate example the copper ring doesn't lose or gain any copper but the copper ring gains a layer of silver - gets silver plated/coated. And the silver rod loses silver but doesn't get plated/coated with anything. So no electrode both simultaneously loses its material  while also gaining a material.

[Hunter2]

At anode a oxidation takes place, on cathode reduction takes place. But a electrode cannot be anode and cathode in same time. So both reaction can not take place on one electrode in same time.

[gavindor]

At anode a oxidation takes place, on cathode reduction takes place. But a electrode cannot be anode and cathode in same time. So both reaction can not take place on one electrode in same time.

I'm not suggesting that any electrode should do both reduction and oxidation at the same time.

I'm saying that in the case of a graphite anode, oxidation takes place  from anions getting oxidised. (when electrons are received from the anions). And the graphite anode doesn't get oxidised when it sends electrons up to the + terminal of the battery.

And in the case of a silver anode,  oxidation takes place  from the  silver anode itself getting oxidised (when electrons are passed to the battery's plus terminal).

I know in the silver nitrate case we get oxidation taking place from the silver anode itself getting oxidised.

When you said that in the silver nitrate case, anions are attracted to the anode, that indicates to me that oxidation is taking place from both those things happening.  A) electrons received from anions so anions oxidising  B) the anode itself oxidising.

Would you agree with that?

And then if so, i'm asking if there are any examples of a silver anode that gets coated by an anion getting oxidised and joining onto it.  (While also the anode shrinks as it itself oxidises while its electrons get sent off to the + terminal of the battery).

(I know in the silver nitrate example the copper ring is a cathode and gets coated from Ag cations that receive an electron, and then cling onto the copper). But I would think there could be electrolysis examples of anions giving off electrons and clinging onto the anode. I know in the lead bromide case you get bromine gas.  If the anode were silver then would you get bromine gas + the silver shrinking down. So oxidation from those two sources?

Thanks

[Hunter2]

Again one is an inert electrode and the other one is an ignoble electrode. So different cases.
At an inert anode only the anions can be oxidised. At an ignoble electrode the Anions react with there material the anion will not oxidised, but the material of the electrode.
At cathode side the cathions will be reduced and coated on it. Doesn't matter inert or ignoble.

[gavindor]

Again one is an inert electrode and the other one is an ignoble electrode. So different cases.
At an inert anode only the anions can be oxidised. At an ignoble electrode the Anions react with there material the anion will not oxidised, but the material of the electrode.
At cathode side the cathions will be reduced and coated on it. Doesn't matter inert or ignoble.

Thanks.. So from that it sounds like you mean that in regard to the anode,  it's one or the other.

Either you get anions going to the anode (like with graphite anode in lead bromide)

Or you get the anode itself shrinking down, (like with silver anode in silver nitrate)

So I don't understand what you meant though when you wrote earlier "Also in the silver case ions involved. The nitrate ions.
Nitrate travels to plus and catch the silver and release one electron into the electrode."

In the silver nitrate case, are you saying that the anions give an electron to the silver electrode? 

If the silver electrode was inert, which it isn't, then it'd not get oxidised or reduced . And if the silver electrode were not inert then it'd get reduced, but we know the silver anode doesn't get reduced. 'cos it's an anode and an anode doesn't get reduced and no reduction takes place at an anode.

In the case of the silver nitrate, I know for sure the silver anode diminishes.  But there you seem to be saying that anions lose electrons to it and the anions get oxidised.  So it sounded to me like you were saying both oxidation processes happen.  Though now I know you're not saying that.

So i'm a bit puzzled by that statement..  Were you saying that Nitrate anions are attracted to the silver electrode? And were you saying they get oxidised?

And wouldn't you agree that the silver anode gets oxidised when it gives electrons to the battery's + terminal.

But then that sounds to me like oxidation going on twice so I don't think you're saying that happens.  I think we agree oxidation of the silver anode the silver anode reduces, and anions don't get oxidised there. 

So i'm a bit puzzled by what you're saying there in the earlier thing you wrote "Also in the silver case ions involved. The nitrate ions. Nitrate travels to plus and catch the silver and release one electron into the electrode."

[Hunter2]

You have Ag anode and AgNO3 means Ag+ and NO3 - in the solution. The cathode is a copper Ring

So if you put a voltage to anode and cathode. The NO3- travel to the Ag anode and create AgNO3, one electron goes into it and travel to the  + of battery.

In formula

Ag + NO3- => AgNO3 + e -

So if AgNO3 in solution is Ag+ + NO3-

Then the formula above would be

Ag + NO3- => Ag+ + NO3- + e-

You can erase the NO3-

You get the main reaction Ag => Ag+ + e-

On cathode side You get AgNO3 + e- => Ag + NO3-

Same like above gives Ag+ + e- => Ag plated on the copper

So the nitrate ship the electrons like boats, but don't get oxidised or reduced.


With PbBr2  you get Pb2+ + 2 Br- if melted.

On Anode 2 Br- => Br2 + 2 e- Graphite will not oxidised, but the Bromide to bromine.
.

On cathode side PbBr2 + 2 e- => Pb + 2 Br-

Pb2+ + 2 Br2- + 2e- => Pb + 2 Br-

Means Pb2+ + 2e- => Pb

Lead get coated.

So Bromide is carrier of the electrons, but also will consumed by oxidising.

I hope its clear now.

[gavindor]

thanks, I will give it some thought