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Topic: DOUBTS ON ELECTROCHEM ETC  (Read 3152 times)

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Offline viera123

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DOUBTS ON ELECTROCHEM ETC
« on: November 10, 2007, 12:03:29 AM »
1. How to predict the colour of salts or metals?

2. When will electrode dissolve into electrolyte?

Offline DevaDevil

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Re: DOUBTS ON ELECTROCHEM ETC
« Reply #1 on: November 12, 2007, 04:47:38 PM »
colors are hard to predict. Most crystalline salts are transparent, where more amorphous salts tend to be opaque.

Some salts from a certain metal have a tendency to be a certain color when soluted, like a copper salt tends to be blueish in water. Nickel salts tend to be greenish. etc.

But for chromium salts / complexes for example you have a color range. Yellow, orange, green


As for when will an electrode dissolve: I gather you mean a metallic electrode?
In that case it will dissolve if the open circuit potential of the cell is enough for the metal to oxidise. In other words if there is a counter reaction to M --> M+ + e- with the right potential to make the reaction possible. Look at the contents of your cell and grab a table of reduction potentials to check that.

Some special complexing reactions will not be noted though (like Pd will dissolve slowly in a nitride solution), but most basic oxidations are in there.

Offline ARGOS++

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Re: DOUBTS ON ELECTROCHEM ETC
« Reply #2 on: November 12, 2007, 05:04:24 PM »

Dear Viera123;

Don’t forget that you can force the electrode to the electrolyte with the same reaction equation by using an outer electrical potential (= electroplating) of correct polarity.


Good Luck!
                   ARGOS++

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