Talk:Galvanic cell

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Contents 1 Mistakes Found 2 Electrochemical potential 3 Few questions 4 Comments 5 Merge with Galvonic corrosion 6 not neccessarily two different metals 7 Clarification Request 8 Errors 9 English Picture

[edit] Mistakes Found

Does anybody notice that in the half ionic equation for the ionization of zinc in the cell, that should be:

           Zn → Zn+2 + 2e-

Zinc would lose electrons more readily than Copper as it has a higher position in the electronchemical series(E.C.S.).Narold 13:59, 6 February 2007 (UTC)

[edit] Electrochemical potential

Can we get some info about the different voltages created by different types of metals? There must be some number for this. - Omegatron 19:07, Feb 11, 2005 (UTC)

See the table at standard electrode potential.

"Galvanic anodes are designed and selected to have a more "active" voltage (technically a more negative electrochemical potential) "

Yeah! that number.

math would be nice.

[edit] Few questions

"The Galvanic cell, named after Luigi Galvani, consists of two metals connected by an electrolyte which forms a salt bridge between the metals. It is also known as a voltaic cell and an electrochemical cell."

1. As far as I know, the galvanic cell contains 2 electrolytes.

Meaning that when the solutions are CuSO₄ and ZnSO₄, there would be both a copper electrolyte and a zinc one? As there is a copper electrode and a zinc electrode? The definition of electrolyte is not clear- here or on it's page. Loggie

2. I've never heard those two electrolytes being referred to as a salt bridge. Salt bridge is a replacement to the porous disk, the device that lets one to connect the two electrolytes without mixing.

Yes- a salt bridge allows ions to travel from one solution to another- it is not connected/ made out of metal, as is suggested. Loggie

3. Shouldn't the voltaic, galvanic and electrochemical cell articles be merged into one?

Are there slight differences between the three, or all they all names for the same item? Loggie

An electrochemical cell can mean a galvanic cell, or be a general term for galvanic and electrolytic cells. Basically, a galvanic cell generates an electromotive force through a spontaneous redox reaction, where electrolysis requires an external current before the reaction will occur. splintax ^(talk) 07:27, 23 May 2006 (UTC)

[edit] Comments

You guys are just not correct in the "Description" part of the Galvanic Cell:

At the Zn anode, an atom of the the metal electrode gives up two electrons, becomes ionized ( forms a positively-charged Zn cation, Zn⁺² ), and goes into the electrolyte solution, where the new cation formed is balanced by a negatively-charged sulfate anion ( SO4^-2 ) coming over through the porous plate (or the salt bridge).

At the same time, at the copper cathode, a positively-charged Cu cation ( Cu⁺² ) in the electrolyte solution picks up the two electrons that came over in the wire from the Zn side of the cell at the surface of the Cu metal electrode. This converts the cation to a neutral Cu metal atom, which plates out onto the Cu electrode (Zn does NOT plate onto the copper cathode). Since a cation disappears from the Cu⁺² electrolyte solution, and a new cation appears in the Zn⁺² electrolyte solution, a sulfate anion ( SO4^-2 ) can cross the salt bridge to balance the change in the positive charges in the two electrolyte solutions.

The statements in the first paragraph are not true. For every neutral Zn atom that dissolves in the ZnSO4 electrolyte, a Cu⁺² cation from the CuSO4 electrolyte plates out onto the copper electrode. The two electrons given up from the Zn side of the cell travel through the wire, do useful work, then enter the Cu electrode and convert a Cu⁺² cation from the electrolyte solution to a neutral Cu atom that sticks to the Cu electrode. At the same time, one SO4^-2 anion moves through the salt bridge from the Cu side to the Zn side to balance the change in the number of cations in the two electrolyte solutions.

The picture, "Scheme Of A Galvanic Cell" should be changed: the right-pointing arrow and the words "Cation flow" should be removed.

The main point in a galvanic cell is that everything has to balance: the number of electrons given up and accepted has to be equal, the charge changes have to balance, and the anions on either side of the bridge have to balance.

Also, the number of electrons involved in the two half-reactions and the energy of those electrons (electrode potential) are two different things entirely. The potential (EMF or voltage) has to do with the nature of the two dissimilar metals; the number of electrons transferred have to do with how many electrons the metals normally lose or gain in chemical reactions.

Starting at "In this way the anode is consumed or corroded....", the rest of the statements in the section are correct.

Also:

In the section "Electric Potential Of A Galvanic Cell", the net reaction shown isn't correct. It should be:

           Cu+2 + Zn -> Cu + Zn+2

A suggestion:

Find a chemist to help you two write this topic.
Old_Chemist

68.225.187.87 10:33, 20 September 2005 (UTC)Alan Speigel (speigela@lycos.com)

---

Alan's observations make sense to me indeed, I simply corrected the following typo: "...one SO4⁺² anion moves..." to "...one SO4^-2 anion moves...".

One thing is unclear to me though, why is it the SO4^-2 ion which crosses the porous separator leftwards to keep the electrolyte compartments neutral, couldn't it be a Zn⁺² crossing rightwards? Michel jullian mj@exbang.com 15:57, 9 December 2005

IIRC, both happen. Sulphate ions move to the left, and zinc ions move to the right. splintax ^(talk) 07:28, 23 May 2006 (UTC)

Hmmmmm....not much of a "separator", then, is it? ("Porous", indeed!) So we have Alan Speigel saying zinc cations don't flow toward the cathode (to the right), and Splintax saying they do. No wonder I'm confused! 24.6.66.193 09:40, 20 April 2007 (UTC)

It may make more sense to change the diagram of the cell to one that is labeled in English, as this is the English wikipedia. —Preceding unsigned comment added by Thisnamenowtaken (talk • contribs) 03:16, 14 March 2008 (UTC)

[edit] Merge with Galvonic corrosion

For one thing, I'm not sure that Galvonic is the correct spelling so who's going to find it there. It's an orphan, it's short, and it would fit in nicely here. Waerloeg 09:26, 25 February 2007 (UTC)

• Oppose - I'd move it to fix the spelling, but it's a distinct enough topic that it deserves a separate article, in my opinion. Dicklyon 17:19, 25 February 2007 (UTC)
• Oppose Support - "galvonic" must die. --Wtshymanski 03:34, 26 February 2007 (UTC)

Galvonic will die, independent of this merge discussion; but please don't move it again manually, as that detaches the page from its history. Dicklyon 04:06, 26 February 2007 (UTC)

But there was no significant history - and if you were mad enough to type in "galvonic corrosion" and bypass the redirect you can see what little history there was. "Galvanic corrosion" is a different page with a different history. --Wtshymanski 04:09, 26 February 2007 (UTC)

OK, whatever; change it that way if you like, but then remove the move request, too. Dicklyon 04:18, 26 February 2007 (UTC)

• While Wikipedia is not a democracy and anyone can edit and guidelines aren't binding and Dicklyon's argument "it's a distinct enough topic" is persuasive...Isn't less than a day too fast to kill merge tags? I like to do useful things before I forget about them and watchlists can remind me without needing to do something instantly. Waerloeg 05:11, 26 February 2007 (UTC)

Yes, we were both overly hasty. Sorry. At this point there's no longer a clear consensus, so we should wait and see. Dicklyon 05:48, 26 February 2007 (UTC)

• Oppose - Sufficiently distinct to merit separate articles. 64.40.60.9 09:30, 21 March 2007 (UTC)

[edit] not neccessarily two different metals

The following point was raised on the talk page for Electrolytic cell:

A galvanic cell could also use the same metal but with different ion concentrations in solution, or maybe even with only a difference in the solution medium (ionic strength, complexing agents, etc.)

--Spoon! 11:57, 6 March 2007 (UTC)

[edit] Clarification Request

If Zn⁺² crosses the porous barrier rightwards, as was stated above, and as is indicated by the "Cation flow" arrow in the diagram, then wouldn't that cause the solution in the right half of the cell to become contaminated with Zinc Sulfate? Does that happen in actual practice?

If so, it would be helpful to state explicitly that it's the Zinc that disolves more quickly than the Copper in this configuration, and that it's this faster dissolution that produces the abundance of electrons at the Zinc anode, relative to the electrons produced at the more slowly dissolving Copper cathode. ( This IS correct, yes? ) When I first looked at this diagram I imagined that the Copper cathode would also (as the entry says all metals do) "become positive ions upon dissolving, and leave electrons behind", thus giving it a negative charge, just like the Zinc anode. It took me a while to figure out that even if that's so, it's the *relative* difference in the rates of electron "production" in each half-cell that gives rise to the current flow from anode to cathode. [ Edited by author on 16 March 2007 for concision only. ] Scott W. 64.40.60.154 15:03, 2 March 2007 (UTC) & 64.40.62.157 09:10, 16 March 2007 (UTC)

The copper cathode doesn't dissolve; on the contrary, it grows. --Spoon! 11:46, 6 March 2007 (UTC)

[edit] Errors

This article contains errors. For example, the diagram is of a Daniel cell. There may be a difference between US usage and UK usage but, in my experience, a cell for producing electricity has always been called a Voltaic cell. Having read the articles for Alessandro Volta and Luigi Galvani I think the term Voltaic cell is much more appropriate. Biscuittin 17:29, 1 June 2007 (UTC)

[edit] English Picture

Can someone find/make a diagram with English labels?Terrx (talk) 21:23, 1 May 2008 (UTC)