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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Mr. Raru on April 23, 2006, 08:33:12 AM

Title: Electrolysis of AgNO3
Post by: Mr. Raru on April 23, 2006, 08:33:12 AM
In the electrolysis of AgNO3 with inert electrodes, why is the silver ion reduced rather than the nitrate ion when the nitrate has a higher standard electrode potential?
Title: Re: Electrolysis of AgNO3
Post by: Bakegaku on April 23, 2006, 01:13:11 PM
A substance is reduced when electrons (or just one) are added to it.  Which ion can accept electrons?
Title: Re: Electrolysis of AgNO3
Post by: Mr. Raru on April 23, 2006, 05:43:05 PM
A substance is reduced when electrons (or just one) are added to it.  Which ion can accept electrons?

Yes, I know this but:
NO3-(aq) + 4H+(aq) + 3e- -> NO(g) + 2H2O(l)   0.96
Ag+(aq) + e- -> Ag(s) 0.80

Ah, but I think I answered my own question. I am not in acidic solution, correct? so the reduction of nitrate is not possible. And Ag+ is more readily reduced than H2O to H2.
2H2O(l) + 2e- -> H2(g) + 2OH-(aq) -0.83

Title: Re: Electrolysis of AgNO3
Post by: AWK on April 24, 2006, 08:42:39 AM
During electrolysis you have anions close to anode and cations close to cathode. During electrolysis of AgNO3 you should add some acid (HNO3) to prevent precipitation of Ag2O.
Title: Re: Electrolysis of AgNO3
Post by: xiankai on April 25, 2006, 05:13:06 AM
just wondering, how does the Ag2O form? isnt Ag supposed to be a non-reactive metal?
Title: Re: Electrolysis of AgNO3
Post by: Alberto_Kravina on April 25, 2006, 07:51:57 AM
just wondering, how does the Ag2O form? isnt Ag supposed to be a non-reactive metal?
Ag2O exists. Although silver is a "non-reactive" metal it forms ions (Au, Pt, and some other "non-reactive" metals form ions as well)
Title: Re: Electrolysis of AgNO3
Post by: AWK on April 25, 2006, 09:08:38 AM
During electrolysis you have cathode compartment and anode compartment.
At cathode the following reactions take place
Ag+ + e = Ag(s)
and
2H2O(l) + 2e- = H2(g) + 2OH-(aq)
without mixing of solution from both compartment
2Ag+ + 2OH- = Ag2O(s) + H2O as a side reaction
when mixing
OH- + H3O+ = 2H2O

At anode
6H2O = O2 + 4H3O+ + 4e-