basic electrolysis

Hello

On a diagram such as the one on this page
http://www.practicalchemistry.org/experiments/quantitative-electrolysis-of-aqueous-copperii-sulfate,154,EX.html, is the cathode attached to the red/positive terminal of the battery? Is the short bar in the cell symbol the positive terminal.

Thanks
andiejeAsked:
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d-glitchConnect With a Mentor Commented:
The definitions of anode and cathode depend on the direction of current flow, not on voltage polarity.
The definition changes depending on the type of cell.

            http://en.wikipedia.org/wiki/Anode

The drawing in the link is correct.  
The anode of the electrolysis cell is attached to the red/positive terminal of the battery.
Current flows from the positive terminal of the battery into the anode of electrolysis cell?
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andiejeAuthor Commented:
Ok. So in a galvanic cell is it correct that the electrode connected to the positive terminus Is the anode and the electrode attached to negative is the cathode
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d-glitchCommented:
Yes.
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andiejeAuthor Commented:
I thought this was the case but I did an experiment today set up like the diagram in the web page whereby the anode was copper foil and the cathode was an iron nail. This was supposed to show electroplating with the anode getting smaller and copper deposited on the iron nail. However brown sludge was deposited on the nail - it didn't look like copper at all.  If I swapped the leads over then something coppery did appear on the nail but the mass of the nail had decreased and the mass of the copper increased suggesting the nail was being chemically eroded in some way.

Is the brown sludge impurities in the copper? Do you need purer copper to show electroplating
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andiejeAuthor Commented:
I thought this was the case but I did an experiment today set up like the diagram in the web page whereby the anode was copper foil and the cathode was an iron nail. This was supposed to show electroplating with the anode getting smaller and copper deposited on the iron nail. However brown sludge was deposited on the nail - it didn't look like copper at all.  If I swapped the leads over then something coppery did appear on the nail but the mass of the nail had decreased and the mass of the copper increased suggesting the nail was being chemically eroded in some way.

Is the brown sludge impurities in the copper? Do you need purer copper to show electroplating
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d-glitchCommented:
Here is a drawing of the setup from Wikipedia.
In your original link,  both electrodes were copper, so it isn't clear what they were trying to do.

The purity of the copper is probably not the issue, but the cleanliness may be.
It may have some coating to protect it from oxidizing.  
The cleanliness of nail is also important.  Sandpaper or Scotchbrite should do the job.
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d-glitchCommented:
>>  it isn't clear what they were trying to do.

Obviously, they were trying to break water in Hydrogen and Oxygen.
That what electrolysis is.
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andiejeAuthor Commented:
In our set up the cathode was iron
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d-glitchCommented:
I left the link out of an earlier post:  http://en.wikipedia.org/wiki/Electroplating

Are you sure the nail is iron?  Steel or stainless steel could be a problem.
Note on the wikipedia page, they say that alloys can cause problems.
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andiejeAuthor Commented:
That's a point. I will look into that tomorrow. It wasn't my experiment. Someone else's wasn't working and they asked me for help and I set it up how I thought it should be and got brown sludge! Will find out about nails and reply tomorrow
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