Voltaic Cells and electron flow

In summary: It will get slightly negatively charged, as Zn2+ from solution will try to deposit on the surface.In summary, electrons flow in a voltaic cell because of the same reaction that occurs when placing a piece of zinc into a solution of copper ions. The separation of the two half cells allows for the artificial separation of the processes of oxidation and reduction. When a wire is attached, the electrons flow from the zinc to the copper electrode, creating voltage and attracting the copper ions. The purpose of the salt bridge is to maintain neutrality in the half cells. In a simple experiment with a zinc electrode and wire, the system will reach equilibrium, with either the zinc ions depositing on the surface or the zinc atoms entering the solution, creating a slight
  • #1
blank_slate
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0
In a voltaic cell, why do electrons flow at all? If I place a piece of zinc metal into a zinc ion solution, nothing happens, right? Likewise if I place a copper electrode into a copper ion solution, nothing happens. When I attach the half cells with something that allows electrons to flow through it, then you get voltage from the electrons of the zinc going to the copper electrode and the copper ions becoming attracted to the electrons. (This is assuming I've attached a salt bridge as well).

My questions is: why does attaching something that allows for the flow of electrons actually mean that any electrons will flow? Why doesn't the zinc half cell and the copper half cell just sit there and nothing happens? The electrons can't be attracted enough to the copper to flow through a wire just to get to the copper ions, can they?

I'm a bit confused. Any help would be great!
 
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  • #2
Think about it this way - if you put piece of zinc into solution of copper ions, you will see reaction, right? Copper will get reduced on the zinc surface. In the voltaic cell exactly the same happens, we just artificially separate places where both processes (oxidation of zinc, reduction of copper) take place. So the reason behind the reaction is the same in both cases.
 
  • #3
It's still a bit odd though. The copper directly interacting with the zinc makes sense, because the actually atoms are interacting, but the voltaic cell is indirect. Yeah the anode has a higher electric potential and such, but just because I stick a wire between them means that electrons will start flowing between them? Obviously that is what's happening, in a sense, but it seems weird.

If I have a zinc electrode placed into zinc ion solution, and stick a wire into it (not connected to anything else, just a wire straight up) do electrons start traveling up the wire then? If so, why? If not, then the there needs to be an attraction that spans the wire or travels through it. I can't seem to get a good grasp of this.

Thanks!
 
  • #4
blank_slate said:
If I have a zinc electrode placed into zinc ion solution, and stick a wire into it (not connected to anything else, just a wire straight up) do electrons start traveling up the wire then? If so, why? If not, then the there needs to be an attraction that spans the wire or travels through it. I can't seem to get a good grasp of this.

Thanks!

Yep. You can test this out for yourself. Take a look at this:

if you attach the negative terminal of a battery to the lead of the electroscope then electrons travel up the wire and when they reach the aluminum foil, the pieces of spread out because electrons repel each other. Similarly if you dip the lead of the electroscope into your zinc electrode/zinc ion half cell, it should spread out a bit. Thats a guess though, I've never tried this before, I'm going to build one of these electroscopes one of these days and start experimenting with it.

To answer your question, the electrons travel up the wire because its not as negatively charged up there. Charge always tries to neutralise itself. If you hook a positive charge up to a wire then electrons from the wire will travel towards the positive charge. The purpose of a battery is it regenerates the charge as soon as its neutralised. The only problem with using a half cell (such as a zinc electrode submerged in a zinc ion solution) is that the build up of positive charge in the solution (which happens because for electrons to leave the zinc metal, zinc cations first have to break off the zinc metal and into the solution) will attract the electrons back into the solution. This is the purpose of the salt bridge. The salt bridge contains anions that can flow into the half cell and keep it neutral. Sorry for giving such a bad explanation there. Its tricky to explain. Took me a good while to get my head around these concepts too. Keep at it and it will all fall into place for you. I learned this by watching youtube videos. I'll try and find the videos I used for you because animations can explain these concepts far better than words can.
 
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  • #5
blank_slate said:
If I have a zinc electrode placed into zinc ion solution, and stick a wire into it (not connected to anything else, just a wire straight up) do electrons start traveling up the wire then?

System will reach some kind of equilibrium. Either Zn2+ from the solution will try to deposit on the surface (charging the wire with +2e), or Zn atoms from the surface will try to get into solution (as Zn2+ - so electrode will be left with 2 excess electrons, that is -2e charge). In fact both things will happen at the same time, just one will dominate (which one depends on the metal and concentration of ions in the solution). That will mean electrode will get slightly charged - and this charge is a source of potential difference. And yes, this charge travels throughout the wire - after all, metals are good conductors.
 
  • #6
CrimpJiggler said:
Similarly if you dip the lead of the electroscope into your zinc electrode/zinc ion half cell, it should spread out a bit.

You will need extremely sensitive electroscope for that to work. But you are right in principle.
 

What is a voltaic cell?

A voltaic cell is a device that converts chemical energy into electrical energy. It consists of two electrodes (typically metals) immersed in an electrolyte solution, which allows for the flow of ions. This creates a potential difference between the two electrodes, causing electrons to flow from one electrode to the other, creating an electric current.

How does electron flow occur within a voltaic cell?

Electron flow occurs within a voltaic cell through a process called oxidation-reduction (redox) reactions. The electrode where oxidation occurs is called the anode, and the electrode where reduction occurs is called the cathode. Electrons flow from the anode to the cathode, creating a current.

What factors affect the rate of electron flow in a voltaic cell?

The rate of electron flow in a voltaic cell can be affected by several factors, including the type of electrodes used, the concentration of the electrolyte solution, the surface area of the electrodes, and the temperature of the cell. A higher concentration of ions and a larger surface area of the electrodes will generally result in a faster electron flow.

How does a salt bridge help to maintain electron flow in a voltaic cell?

A salt bridge is a component of a voltaic cell that helps to maintain electron flow by completing the circuit between the two electrodes. It consists of an inverted U-shaped tube filled with an electrolyte solution, typically a salt bridge. This allows ions to flow between the two half-cells, balancing out the charges and preventing the buildup of excess charge on either electrode.

What are some practical applications of voltaic cells?

Voltaic cells have many practical applications, including powering electronic devices such as calculators, flashlights, and cell phones. They are also used in larger applications, such as powering electric cars and providing backup power for buildings. Additionally, voltaic cells are used in many scientific experiments and can be used to generate electricity from renewable energy sources such as solar and wind power.

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