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Topic: Solubility of Silver Chromate(VI)  (Read 11980 times)

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Offline Donaldson Tan

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Solubility of Silver Chromate(VI)
« on: July 27, 2004, 11:41:20 PM »
Standard QA of Silver Chromate(VI) yields the following the result:

Yellow Precipitate formed upon addition of aq Silver Nitrate, soluble in Nitric Acid and Aq. NH3. I'm not sure why Ag2CrO4 formed dissolves in both HNO3 and NH3.

(1)- 2[CrO4]2- + 2H+ <-> [Cr2O7]2- + H2O
(2)- Ag2CrO4 (s) <-> 2Ag+ (aq) + CrO4^2- (aq)
I think addition of dil. HNO3 favours the forward the reaction of eqbm (1), thus reducing the availability of chromate(VI) ions in the solution, hence more silver chromate(VI) will dissolve, in accordance to Le Chaterlier's Principle acting in Eqbm(2).

In the case of solubility in ammonia, I think it's because of NH3's ability to form diamine silver complex.

Can someone enlighten me?
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Offline Mitch

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Re:Solubility of Silver Chromate(VI)
« Reply #1 on: July 30, 2004, 02:13:53 AM »
I think you nailed the solubility aspect. I'm not quite sure why dilute acid oxidizes Chromium better, but your logic makes sense. I'll look into some Chromium chemistry and see if I can have a better answer for you tomorrow.
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Offline AWK

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Re:Solubility of Silver Chromate(VI)
« Reply #2 on: July 30, 2004, 03:30:15 AM »
First of all - silver chromate is not yellow - it is red-brown. Of course it is soluble in both: HNO3 and NH3, yes, beacuse of forming dichromate anion, and diammine complex, respectively.
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Offline Donaldson Tan

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Re:Solubility of Silver Chromate(VI)
« Reply #3 on: August 27, 2004, 05:07:44 AM »
thank you so much..

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"Say you're in a [chemical] plant and there's a snake on the floor. What are you going to do? Call a consultant? Get a meeting together to talk about which color is the snake? Employees should do one thing: walk over there and you step on the friggin� snake." - Jean-Pierre Garnier, CEO of Glaxosmithkline, June 2006

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