Chemical Electric CELL with graphite electrodes?

[matthew77ask]

In normal chemical cells, the electrodes are two different metals so that the more reactive one gives off electrons and create a flow of electrons and hence electricity. [the electrolyte is say NaOH aq or whatever]

Just wondering - is it possible to have a chemical cell consisting of:
a) Copper / graphite electrodes
b) Zinc / graphite electrodes

The metal in the above - can they give off electrons and becomes ion and create a flow of electrons / electricity?

thanks

 

[Borek]

In normal chemical cells, the electrodes are two different metals

No. Electrodes can be made of metal that dissolves, but they don't have to, they can be inert as well.

 

[matthew77ask]

No. Electrodes can be made of metal that dissolves, but they don't have to, they can be inert as well.

Thanks. If that is the case, can the combination work?

Cu/Graphite; and

Zn/ Graphite

and which is the + terminal and - terminal?

Many thanks

 

[Borek]

Seems to me like you should first do some reading about electrochemistry, asking detailed questions first won't get you far.

You may start with
http://en.wikipedia.org/wiki/Electrochemical_cell
http://en.wikipedia.org/wiki/Electrolytic_cell
http://en.wikipedia.org/wiki/Galvanic_cell

 

[matthew77ask]

I know about how for Mg/Fe cell : -the Mg is more reactive than Fe so gives off electrons and hence becomes the negative electrode.

However, I am confuse with

Cu/Graphite; and

Zn/ Graphite

Because one is metal while the other is not - but just a conductor of electricity.

My guess is that
Cu/Graphite would not work as Graphite is "more reactive" than Cu.

but Zn / Graphite works as Zn is more reactive than Graphite and hence can give off electrons and oxidizes to Zn ion, and becomes the negative terminal.

I Googled - but could not find info on Carbon electrode with Metal as a cell (or maybe the search engine not good enough?)

Am I right? if not please help...

There must be more information that is beyond the O level (which I am teaching) that I may not know of...

Many thanks

 

[Borek]

I am not sure what you mean by Cu/graphite - solid Cu and graphite, or Cu²⁺ and graphite? For the cell (galvanic) to work you need two half reactions. One must be reduction, the other one oxidation. Having just a solution of cation may give you system ready for reduction, but what is going to be oxidized? Try to write reaction equations.

 

[matthew77ask]

I am not sure what you mean by Cu/graphite - solid Cu and graphite, or Cu²⁺ and graphite? For the cell (galvanic) to work you need two half reactions. One must be reduction, the other one oxidation. Having just a solution of cation may give you system ready for reduction, but what is going to be oxidized? Try to write reaction equations.

Sorry, I was not clear...

What I really wanted to find out is :
In chemical Cells - if the electrodes are Copper (solid) and Graphite (instead of the usual cells with two different metals) in a electrolyte of aq NaOH, will it works?

What about if it is Magnesium(solid) and Graphite instead - in the same settings.

I was wondering - the cells work on redox. In Cu / Mg electrodes cell, the more reactive metal Mg oxidizes and gives off electrons and becomes the negative terminal, the electrons than travels to Cu electrode and forms a close circuit with the aq NaOH. and the cell is functioning.

In Copper / Graphite [and Magnesium / Graphite] case mentioned, Graphite is not part of the metal reactivity series. And hence with the Graphite oxidizes and gives off electrons ? It most likely not - as what ions will Graphite form? Then, will the set up actually works?

Would it work for Magnesium / Graphite electrode case? Mg is more reactive, hence oxidises and becomes negative electrode, the electrons then travels to the Graphite electrode into the aq NaOH to form a close circuit... would this be correct way of reasoning?

Very interesting - juz that I do not have a lab to just try it out and confirm if the set up can work or not ?

Anyone can help?

Many thanks...

 

[Borek]

Sorry to say that, but you are wrong in so many ways at the same time I have no idea where to start. You really need a solid course in electrochemistry, and some refresher in general chemistry.

Copper is incompatible with NaOH as electrolyte - you will precipitate hydroxide, leaving no Cu²⁺ in the solution.

Magnesium is a bad idea as well - it is reactive enough to react directly with water, regardless of whether there is copper present or not.

You don't need electrode to reduce or oxidize - while it is one of ways of preparing galvanic cell, it can as well contain system like - say - Ce³⁺/Ce⁴⁺.

You are right about carbon not producing any ions. It doesn't mean there can't be a reaction taking place on its surface.

 

[matthew77ask]

Sorry to say that, but you are wrong in so many ways at the same time I have no idea where to start. You really need a solid course in electrochemistry, and some refresher in general chemistry.

Copper is incompatible with NaOH as electrolyte - you will precipitate hydroxide, leaving no Cu²⁺ in the solution.

Magnesium is a bad idea as well - it is reactive enough to react directly with water, regardless of whether there is copper present or not.

You don't need electrode to reduce or oxidize - while it is one of ways of preparing galvanic cell, it can as well contain system like - say - Ce³⁺/Ce⁴⁺.

You are right about carbon not producing any ions. It doesn't mean there can't be a reaction taking place on its surface.

You are right - I do need an in solid course in electrochemistry.
When I came up with the combinations - my focus is on the graphite electrodes - and the rest of the components was "done in a fly". Thank you for pointing these out like the Cu2+ with NaOH - did not think of that..(now I learn to look deeper again) and about Magnesium with water.

I have learn a lot in your answers.. thanks a lot.

I still am puzzle - can there be a cell with graphite as one electrode and another metal as the other electrode and what would the combination be for that (electrodes , electrolytes etc) ... many thanks for helping me to answer this question