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Topic: Diatomic Aluminum Cation?  (Read 6242 times)

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Kirken

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Diatomic Aluminum Cation?
« on: September 14, 2004, 08:16:08 PM »
The task at hand is to complete the chemical equation and and determine the whether the products form a precipitate from aqueous solution.

Reactants: NaBr + Al2(SO4)2

I am really lost with Al2(SO4)2. As the compound must have a neutral charge, the net charge of the anions must equal the net charge of the cations. As (SO4)2 has a net charge of 4-, with each SO4 having a charge of 2-, Al2 must have a net charge of 4-. This really doesn't make much sense to me, as the aluminum cation has a charge of 3+, and 2 aluminum cations would logically have a charge of 6+, which is unequal to the 4- net charge of (SO4)2. The only diatomic cation my class has been introduced to is the mercurous cation, Hg2 2+, but it seems to me that the only way the compound Al2(SO4)2 makes sense is if Al2 is a diatomic cation with a charge of 4+. Is this so?

As for the products of the reaction, assuming Al2 is a diatomic cation with a 4+ charge, I think they would be Na2(SO4), which I know to be water-soluble, and Al2Br4. I know ionic bromide compounds are generally water-soluble, with the exception of silver, Hg2 2+, and lead salts, but is a bromide salt of a diatomic aluminum cation water-soluble?

Thank you for your time.

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Re:Diatomic Aluminum Cation?
« Reply #1 on: September 14, 2004, 08:43:37 PM »
I think it's a typo.  Should be Al2(SO4)3.  Commonly known as alum, by the way.

Kirken

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Re:Diatomic Aluminum Cation?
« Reply #2 on: September 14, 2004, 09:17:18 PM »
Thanks, that makes sense. I really resent those typos; I spent a good hour researching in both French and English on diatomic/dinuclear cations.

Offline Donaldson Tan

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Re:Diatomic Aluminum Cation?
« Reply #3 on: September 15, 2004, 09:37:18 PM »
I'm sure that one hour is not only frustrating but also well spent, because it teaches you alot of things

 :angel2:
"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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Re:Diatomic Aluminum Cation?
« Reply #4 on: September 17, 2004, 02:48:10 AM »
Should be Al2(SO4)3.  Commonly known as alum, by the way.

This is not alum! - KAl(SO4)2
AWK

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Re:Diatomic Aluminum Cation?
« Reply #5 on: September 20, 2004, 12:35:20 PM »
Doh!  My mistake, sorry.

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