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Topic: dissolution  (Read 4716 times)

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mharden

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dissolution
« on: August 07, 2005, 12:26:10 PM »
In dissoution, the solubility of magnesium carbonate can be increased by acidifying the solution in which it is suspended, this is an example of dissolution via: formation of weak electrolyte, reduction or oxidation of anion, formation of complex ion or changing an ion to another species which is not a weak electrolyte.

I've read on the principle of dissolution and all of the above are ways thisoccurs- by lacing the salt in an acidic solution would this yield for eg a base and a complex ion? thx

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Re:dissolution
« Reply #1 on: August 07, 2005, 12:58:52 PM »
solubility is increase via the formation of complex ion. complex formation can be achieved via chaning the pH of the solution, or by adding reagents that facilitate the complex formation.

eg. Zn(OH)2 dissolves in excess alkali via the formation of zincate anion.
Zn(OH)2 + 2OH- <-> Zn(OH)42-

eg. the solubility of iodine in water is increased by adding iodide ions.
I2 + I- <-> I3-

All these processes are actually chemical equilibrium, and thus best described by the Le Chatelier's Principle.
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Re:dissolution
« Reply #2 on: August 07, 2005, 01:11:20 PM »
solubility is increase via the formation of complex ion.

Not necesarilly - carbonates solubility increase in acidified solutions due to the anion protonation. Removal of the ions that are present in the dissolving substance is what counts, how it is done is less important.
« Last Edit: August 07, 2005, 05:00:07 PM by Borek »
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Re:dissolution
« Reply #3 on: August 07, 2005, 08:15:56 PM »
solubility can also be increased via chemical reaction. an acid solution dissolves water-insoluble base via neutralisation.
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