Electrolytic Reactions: Anode vs Cathode

[shivaniits]

hey guys
i have put this question to clarify some points on battery anode cathode reactions...let me describe this..if we consider the cell to be two electrodes with in between electrolyte ..
at anode one has the situation:
metal=metal ion+electron released
i.e oxidation takes place..!
so why can't these electrons go directly to other electrode through electrolyte and it would be a shorter path too..i am literally confused about a point that if two electrodes are immersed in same electrolyte...which is an excellent conductor should not lead to short circuit and carry the electrons from directly through a shorter path rather than going through the whole circuit..??

 

[Borek]

Electrons can't through the electrolyte - ions can.

In some solvents (like ammonia) solvated electrons are relatively stable, so probably battery made with liquid ammonia would behave slightly differently.

 

[shivaniits]

hi there
ok so electrons can not go though but ions can..is this all happening due to the formation of DL(double layer) that acts as an insulator between electrode and electrolyte..!
http://en.wikipedia.org/wiki/Helmholtz_double_layer

 

[Borek]

No, double layer has nothing to do with the situation.

 

[shivaniits]

No, double layer has nothing to do with the situation.

ok so what it is that's preventing the movement of electrons in electrolyte but yet allows the movement of ions..??
why we observe this kind of behavior..!

 

[Borek]

Electrons are not stable in the solution, they react with water.

Besides, why should they even try to go through the solution if they can go through an external circuit, which has much lower resistance?

 

[shivaniits]

Besides, why should they even try to go through the solution if
they can go through an external circuit, which has much lower resistance?

that's because electrolyte is a good conductor..and if the attached load is of mega ohms or
an other higher value..won't the electrolyte would provide the shorter path between the terminals...!
won't the electrons prefer the shorter path instead of going a way long from one electrode to other..!
besides that one can't completely ignore the fact of electrolyte being conductive..!

 

[Borek]

Electrolyte is not as good conductor as you seem to be thinking, plus - as stated earlier - electrons in the solution would react with water molecules.

 

[nsaspook]

that's because electrolyte is a good conductor..and if the attached load is of mega ohms or
an other higher value..won't the electrolyte would provide the shorter path between the terminals...!
won't the electrons prefer the shorter path instead of going a way long from one electrode to other..!
besides that one can't completely ignore the fact of electrolyte being conductive..!

The electrolyte is a good conductor of ions not electrons so the electrons will only move from the plates with a good conductor of electrons (wire) connected to the plate +- terminals.
http://www.av8n.com/physics/lead-acid.htm

One way to look at this starts by observing that the electrochemical potential is a potential i.e. the energy of the bisulfate ion is a function of position, independent of how the ion got to that position.

The height of this potential can be considered a “barrier” to the reaction.

In equilibrium, i.e. when the cell is open-circuited, the electrochemical potential is everywhere an equipotential, i.e. the height is independent of position. The mystery arises when I place the cell under load. This manifestly shifts the potential. The terminal marked "+" will become less positive, i.e. more negative, becoming unattractive to negatively-charged ions. We can calculate the density of ions using the Boltzmann factor, ρ ∝ exp(−E / kT).

This can be called the "static" or "integral" view of the situation.

 

[DrDu]

No, double layer has nothing to do with the situation.

I am not so sure about that. The double layer guarantees that the interior of the solution is field free. So an electron in the solution would not experience any driving force.

 

[Borek]

I am not so sure about that. The double layer guarantees that the interior of the solution is field free. So an electron in the solution would not experience any driving force.

Same about ions, yet they move.

But I agree I overdid with the answer. What I really meant was that you can answer the question without invoking the double layer.

 

[shivaniits]

The electrolyte is a good conductor of ions not electrons so the electrons will only move from the plates with a good conductor of electrons (wire) connected to the plate +- terminals.

i agree with fact that something being stated as conductor is one that responds to electric field with its own charges..as ions in case of electrolyte and in case of solids in which tere are no free ions the electrons serve as charges for conduction...!
but i am here concerned about the point that if they something is at different potential..within a medium which is rather conductive they are most probable chances of getting them discharged producing static electricity..due to imbalance of charges at different electrodes and since electrolyte is conductive though conducts with help of free ions...they can discharge ..!
but if we take action of double layer it solves a little bit and i am not considering here conduction through electrons in electrolyte rather referring conduction through ions in electrolyte..!the double layer makes the rest of electrolyte unaffected by potential hence when is not in circuit the electrodes are at different potentials but can't discharge unless we provide a path...through interconnecting them in a circuit..!

 

[Borek]

Basically what you wrote is "double layer makes the solution non conducting, so when we close the circuit current flows from the electrode to electrode". Well, if the solution is not conductive, circuit is not closed, so the current doesn't flow. To close the circuit you need the conductivity of the solution.

 

[shivaniits]

Basically what you wrote is "double layer makes the solution non conducting

no what i actually wanted to refer is that double layer helps or actually shields the electrodes allowing the discharge only through connecting wires..!
although it doesn't allows passage of electrons but still because of ions it is still conductive..!

so on the overall this dl thing helps to understand a little bit but what if we have to look though another perspective..!