ALuminum reactions with reagents

  • #1
I'm having extreme difficulty identifying some precipitates I obtained from combining a solution of Aluminum Nitrate and Sodium Carbonate. The result was an orange precipitate. I have searched high and low (complex ions, decomposition, redox, etc) but I can't figure it out. Please HELP!
 

Answers and Replies

  • #2
chemisttree
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Are you sure the sodium carbonate wasn't really sodium chromate or dichromate? What color were the two solutions before you combined them?
 
  • #3
i did have a reaction with chromate too, but i had another with clear sodium carbonate and aluminum nitrate and got an orange ppt. I was thinking it could be Al2O3? i just don't know how that could occur.
 
  • #4
Borek
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Most Al precipitates I can think off are white. Carbonate is one of them. IMHO if it was orange, you may have mislabelled solutions or you did some other mistake.
 
  • #5
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Its been awhile since I was doing redox reactions, but I'm presuming the reaction took place in the presence of water. If so the Aluminium Nitrate should undergoe a redox reaction with the water.

Half equations:
2H2O(l) -> O2(aq) + 4H+(aq) + 4e-
Al3+(aq) + 3e- -> Al(aq)

Full equation:
6H2O(l) + 4Al3+(aq) -> 2Al2O3(s) + 4H+(aq)

The Aluminium and Water react due to their electronegativity.
 
  • #6
chemisttree
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Its been awhile since I was doing redox reactions, but I'm presuming the reaction took place in the presence of water. If so the Aluminium Nitrate should undergoe a redox reaction with the water.

Half equations:
2H2O(l) -> O2(aq) + 4H+(aq) + 4e-
Al3+(aq) + 3e- -> Al(aq)

Full equation:
6H2O(l) + 4Al3+(aq) -> 2Al2O3(s) + 4H+(aq)

The Aluminium and Water react due to their electronegativity.
None of this happens....
 
  • #7
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i did have a reaction with chromate too, but i had another with clear sodium carbonate and aluminum nitrate and got an orange ppt. I was thinking it could be Al2O3? i just don't know how that could occur.
In this conditions should precipitate Al(OH)3 (white) which easily include impurities; infact this precipitation it's used to purify water. A small, not initially visible amount of coloured substance (chromate, for example) easily gives a colour to the precipitate.
 

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