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Author Topic: What are the principles of electrolysis?  (Read 5197 times)

Gerald McCollum

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What are the principles of electrolysis?
« on: 18/03/2009 05:30:03 »
Gerald McCollum  asked the Naked Scientists:
   
I have a question about electrolysis.

Basically, everything about the process.   I know the basics of needing a DC power source, two electrodes, a liquid medium to place the electrodes into and an understanding about the reactivity of metals.

Since I am new to this, I do not know the details. How much voltage to apply for a certain amount of time for a measured thickness of deposit on the cathode, or what would be the best salt solution of a particular metal to use? Or would applying heat to the electrolyte solution help or hurt the process?  

When trying to form a specific metal deposit on an electrode what is the best metal solution to use? Example: If I wanted to deposit a thin layer of magnesium or tin or zinc or bismuth or silver, etc what would be the best electrolyte to use?
 
As I said, I am new to this and I know a little about the basics, but I don't know about the specifics of how much voltage, percentage of solution, time per thickness of a metal layer deposited on an electrode and other specifics that I haven't mentioned here.
   
Is there a place online that would have the specifics that I am looking for and/or can you provide some answers?

Thank you very much.
 
Gerald
USA

What do you think?


 

Offline Raghavendra

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What are the principles of electrolysis?
« Reply #1 on: 23/03/2009 10:58:47 »
hmmmm
 

Offline lancenti

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What are the principles of electrolysis?
« Reply #2 on: 23/03/2009 12:51:21 »
Since I am new to this, I do not know the details. How much voltage to apply for a certain amount of time for a measured thickness of deposit on the cathode, or what would be the best salt solution of a particular metal to use? Or would applying heat to the electrolyte solution help or hurt the process?   

The current is more important than the voltage for this, and while I'm sure you can convert that voltage into current via the equation V = IR, I'm not too sure at the moment.

Anyway, if we take silver for example:

Ag+ + e- → Ag

So basically the rate at which I deposit Silver depends on how fast this reaction happens, i.e. how much current is driven through the system. To work out how big a current I need given the amount of time I have, I need to know the following:

1. Density of Silver (ρ, 10.5 g cm-3)
2. Surface Area to be plated (A)
3. Ar of Silver (107.9 g mol-1)

So we could do this the long way...

Q = It (Charge = Current x Time)
N = Q/e = It/e (Number of Electrons or Silver Atoms formed = Charge / Elementary Charge)
N = Aρ/Ar (Number of Silver Atoms Required per cm = Surface Area x Density of Silver

So per cm of thickness, I need to deliver:
It/e = Aρ
I = (Aρe/Art) Amperes of Current.

The short way would involve using Faraday's Constant, 96500 Coulombs per Mole. The maths is similar.
« Last Edit: 23/03/2009 12:53:22 by lancenti »
 

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What are the principles of electrolysis?
« Reply #2 on: 23/03/2009 12:51:21 »

 

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