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Aluminium oxide is an amphoteric substance, meaning it can react with both acids and bases, such as hydrofluoric acid and sodium hydroxide, acting as an acid with a base and a base with an acid, neutralising the other and producing a salt. Al 2 O 3 + 6 HF → 2 AlF 3 + 3 H 2 O Al 2 O 3 + 2 NaOH + 3 H 2 O → 2 NaAl(OH) 4 (sodium aluminate)
Closely related are aluminium oxide hydroxide, AlO(OH), and aluminium oxide or alumina (Al 2 O 3), the latter of which is also amphoteric. These compounds together are the major components of the aluminium ore bauxite. Aluminium hydroxide also forms a gelatinous precipitate in water.
The following chart shows the solubility of various ionic compounds in water at 1 atm pressure and room temperature (approx. 25 °C, 298.15 K). "Soluble" means the ionic compound doesn't precipitate, while "slightly soluble" and "insoluble" mean that a solid will precipitate; "slightly soluble" compounds like calcium sulfate may require heat to precipitate.
A solution containing an aqua ion does not have the long-range order that would be present in a crystal containing the same ion, but there is short-range order. X-ray diffraction on solutions yields a radial distribution function from which the coordination number of the metal ion and metal-oxygen distance may be derived. With aqua ions of high ...
Al + NaOH + H 2 O → NaAlO 2 + 3 / 2 H 2. although the aluminium species in solution is probably instead the hydrated tetrahydroxoaluminate anion, [Al(OH) 4] − or [Al(H 2 O) 2 (OH) 4] −. [2] Oxidizing acids do not effectively attack high-purity aluminium because the oxide layer forms and protects the metal; aqua regia will
As per researches conducted by V.K.Chhabra, Chief Chemist (retd.) P.H.E.D. Rajasthan, activated alumina, when used as a fluoride filter, under field conditions can best be regenerated by a solution of lye (sodium hydroxide; NaOH), sulfuric acid (H 2 SO 4). The fluoride uptake capacity (FUC) of commercial activated alumina can be up to 700 mg/kg.
Pure cryolite has a melting point of 1009 ± 1 °C (1848°F). With a small percentage of alumina dissolved in it, its melting point drops to about 1000 °C (1832°F). Besides having a relatively low melting point, cryolite is used as an electrolyte because, among other things, it also dissolves alumina well, conducts electricity, dissociates electrolytically at higher voltage than alumina, and ...
The extraction process (digestion) converts the aluminium oxide in the ore to soluble sodium aluminate, NaAlO 2, according to the chemical equation: Al(OH) 3 + NaOH → NaAlO 2 + 2 H 2 O. This treatment also dissolves silica, forming sodium silicate : 2 NaOH + SiO 2 → Na 2 SiO 3 + H 2 O. The other components of Bauxite, however, do not dissolve.