The discussion centers on the unexpected formation of an orange precipitate when combining Aluminum Nitrate and Sodium Carbonate. Participants suggest the possibility of mislabeling the reagents, particularly considering the potential presence of chromate ions. The chemical reactions involved include redox processes where Aluminum Nitrate reacts with water, leading to the formation of Aluminum Oxide (Al2O3) and the release of protons. The conversation emphasizes the importance of reagent identification and the impact of impurities on precipitate coloration.
PREREQUISITESChemistry students, laboratory technicians, and researchers involved in inorganic chemistry and precipitate analysis will benefit from this discussion.
+Minkie+ said: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.
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.mavsqueen06 said: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.