Search results
Results from the WOW.Com Content Network
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)
Aluminium hydroxide gels can be dehydrated (e.g. using water-miscible non-aqueous solvents like ethanol) to form an amorphous aluminium hydroxide powder, which is readily soluble in acids. Heating converts it to activated aluminas, which are used as desiccants , adsorbent in gas purification, and catalyst supports .
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 metal ion in aqueous solution or aqua ion is a cation, dissolved in water, of chemical formula [M(H 2 O) n] z+.The solvation number, n, determined by a variety of experimental methods is 4 for Li + and Be 2+ and 6 for most elements in periods 3 and 4 of the periodic table.
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.
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
The water in the air actually sticks to the alumina itself in between the tiny passages as the air passes through them. The water molecules become trapped so that the air is dried out as it passes through the filter. This process is reversible. If the alumina desiccant is heated to ~200 °C, it will release the trapped water.
Metal oxides which react with both acids as well as bases to produce salts and water are known as amphoteric oxides. Many metals (such as zinc, tin, lead, aluminium, and beryllium) form amphoteric oxides or hydroxides. Aluminium oxide (Al 2 O 3) is an example of an amphoteric oxide. Amphoterism depends on the oxidation states of the oxide.