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[3] [4] It is a basic oxide dissolving in acids to give solutions of vanadium (III) complexes. [4] V 2 O 3 has the corundum structure. [ 4 ] It is antiferromagnetic with a critical temperature of 160 K. [ 5 ] At this temperature there is an abrupt change in conductivity from metallic to insulating. [ 5 ]
Vanadic acid, H 3 VO 4 exists only at very low concentrations because protonation of the tetrahedral species [H 2 VO 4] − results in the preferential formation of the octahedral [VO 2 (H 2 O) 4] + species. In strongly acidic solutions, pH < 2, [VO 2 (H 2 O) 4] + is the predominant species, while the oxide V 2 O 5 precipitates from solution at ...
If acid is slowly added to a solution of Na 3 VO 4, the colour gradually deepens through orange to red before brown hydrated V 2 O 5 precipitates around pH 2. These solutions contain mainly the ions HVO 4 2− and V 2 O 7 4− between pH 9 and pH 13, but below pH 9 more exotic species such as V 4 O 12 4− and HV 10 O 28 5− ( decavanadate ...
In strongly acidic solutions, pH < 2, [VO 2 (H 2 O) 4] + is the predominant species, while the oxide V 2 O 5 precipitates from solution at high concentrations. The oxide is formally the acid anhydride of vanadic acid. The structures of many vanadate compounds have been determined by X-ray crystallography.
Acidic oxides will typically have a low pK a and may be inorganic or organic. A commonly encountered acidic oxide, carbon dioxide produces an acidic solution (and the generation of carbonic acid) when dissolved. Generally non-metallic oxides are acidic. [2] The acidity of an oxide can be reasonably assumed by its accompanying constituents.
At 25 °C (77 °F), solutions of which the pH is less than 7 are acidic, and solutions of which the pH is greater than 7 are basic. Solutions with a pH of 7 at 25 °C are neutral (i.e. have the same concentration of H + ions as OH − ions, i.e. the same as pure water). The neutral value of the pH depends on the temperature and is lower than 7 ...
Another possibility is the molecular autoionization reaction between two water molecules, in which one water molecule acts as an acid and another as a base. H 2 O + H 2 O ⇌ H 3 O + + HO −. The bicarbonate ion, HCO − 3, is amphoteric as it can act as either an acid or a base: As an acid, losing a proton: HCO − 3 + OH − ⇌ CO 2− 3 ...
A basic oxide, also called a base anhydride (meaning "base without water"), is usually formed in the reaction of oxygen with metals, especially alkali (group 1) and alkaline earth (group 2) metals. Both of these groups form ionic oxides that dissolve in water to form basic solutions of the corresponding metal hydroxide: Alkali metals (Group 1)