Thursday 19 March 2015

inorganic chemistry - Is iron(III) carbonate stable in water?


I searched for this onsite already, and also found the following answer on Quora:



In aqueous environment, iron(III) is bound by water molecules and exists as $\ce{[Fe(H2O)6]^3+}$. Due to strong interaction between Fe(III) and some of the aqua ligands, the complex can dissociate into $\ce{[Fe(OH)_n(H2O)6^{n-}]3^{n-}}$ and $\ce{H+}$. Carbonate is a base, so it will capture proton and further facilitate the formation of hydroxyl complexes so much that it will produce $\ce{H2CO3}$ and $\ce{Fe(OH)3}$, the former eventually decomposes into water and $\ce{CO2}$. Therefore, iron(III) carbonate cannot exist in water.



In solid state, most of iron(III) compounds are hygroscopic, which means that they have strong affinity for moisture. And of course, when water gets involved, the above processes start happening, which eventually decomposes iron(III) carbonate, if it could ever be formed as solid.


Therefore, the compound itself is not stable in solutions or in solid states.



Is this correct? What happens in the following equation then:


$$\ce{2 FeCl3(aq) + 3 Na2CO3(aq) -> Fe2(CO3)3 + 6 NaCl}$$


Will we get different end products? What will be solid? Hydroxides or oxides? Will there be carbon dioxide evolved? Are any of the products going to be hydrates?




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