Chemical Forums
Chemistry Forums for Students => Inorganic Chemistry Forum => Topic started by: Datura on June 13, 2005, 02:07:11 PM
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Hi,
When putting together the solutions of AgNO3, acetic acid, ammonia and hydrazine, a solid silver will form preferably on the solid gold (or any metal?) that is put into the solution. I am confused about the redox reactions taking place here, and the role of the four components in the solution???
My own thoughts about it: The combination of AgNO3 and ammonia looks like the "Tollens reagent" which forms [Ag(NH3)2]NO3 (aq). I remember having read that hydrazine is a reductor. So that could mean that at the catalytic gold surface:
[Ag(NH3)2]NO3 (aq) + NH2NH2 => Ag(s) + water + a lot of ammonia
How can this happen?
Would anyone know the influence of acetic acid on this reaction? I noticed that the reaction quickens and the silver is deposited more homogeneous. Without the acetic acid immediately yellow stuff appears in the solution, some kind of silver salt?
Anyone any ideas? :)
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pH adjusting?
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The combination of ammonia and acetic acid just for regulation of the pH? Actually the pH is very high, estimated pH=11. So what happens if the pH is getting higher, would that promote the redox reaction?
Now, it looks to me like the silver and ammonia initially form this Tollens complex, which is reduced by hydrazine. And the reaction is controlled by the pH of the solution. Does that makes sense?