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Are the chemicals $\ce{Fe(OH)3}$ and $\ce{Fe2O3⋅3H2O}$ equivalent? They are both network solids and have the same empirical formula but I know that doesn't always mean they are structurally the same.

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    $\begingroup$ I'd rather not use long words. These two are the same. $\endgroup$ Nov 13 '20 at 11:05
  • $\begingroup$ Note that iron(III) hydroxide/hydrated oxide, or more generally all/most such substances of transient metals, do not have well defined structure nor composition. $\endgroup$
    – Poutnik
    Nov 13 '20 at 11:42
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    $\begingroup$ Our lab did over a thousand XRD patterns of corrosion deposits and these compound patterns often showed up , Technicians spent hours with the Fink Index trying to separate them . From a practical corrosion prevention perspective , it makes no difference. $\endgroup$ Nov 13 '20 at 17:13
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Fe(OH)3 is iron(III) hydroxide, which is a form of iron hydroxide and is different from anhydrous iron(III) oxide (which is Fe2O3) and hydrated iron(III) oxide (which is Fe2O3·nH2O, where n, in this case is 3). See the list of iron oxides and iron hydroxides. Also see this Wikipedia article which says,

Several hydrates of Iron(III) oxide exists. When alkali is added to solutions of soluble Fe(III) salts, a red-brown gelatinous precipitate forms. This is not Fe(OH)3, but Fe2O3·H2O (also written as Fe(O)OH). Several forms of the hydrated oxide of Fe(III) exist as well.

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