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It forms a hexahydrate with the formula [Al(H 2 O) 6]Cl 3, containing six water molecules of hydration. Both the anhydrous form and the hexahydrate are colourless crystals, but samples are often contaminated with iron(III) chloride, giving them a yellow colour. The anhydrous form is commercially important. It has a low melting and boiling point.
The first solvation shell of a sodium ion dissolved in water. An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, also known as sodium chloride (NaCl), in water would be represented as Na + (aq) + Cl ...
Crystallographic analysis reveals that the solid consists of [trans-NiCl 2 (H 2 O) 4] subunits that are hydrogen bonded to each other as well as two additional molecules of H 2 O. Thus one third of the water molecules in the crystal are not directly bonded to Ni 2+, and these might be termed "water of crystallization".
A combined IR, Raman, X-ray, and neutron diffraction study of concentrated hydrochloric acid showed that the hydronium ion forms hydrogen bonded complexes with other water molecules. [28] (See Hydronium for further discussion of this issue.) The pK a value of hydrochloric acid in aqueous solution is estimated theoretically to be −5.9. [5]
anhydrous Having or containing no water molecules, referring especially to water of hydration. [4] Because many processes in chemistry are impeded in the presence of water, it is often of critical importance that water-free reagents and techniques are used. Anhydrous compounds tend to gradually absorb water from the atmosphere.
To clarify that it is the gaseous form that is being referred to, the term anhydrous is prefixed to the name of the substance: Gaseous ammonia is generally referred to as anhydrous ammonia, to distinguish it from its solution in water, household ammonia solution, also known as ammonium hydroxide.
The water molecule is amphoteric in aqueous solution. It can either gain a proton to form a hydronium ion H 3 O +, or else lose a proton to form a hydroxide ion OH −. [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 ...
The two main oxide-hydroxides, AlO(OH), are boehmite and diaspore. There are three main trihydroxides: bayerite, gibbsite, and nordstrandite, which differ in their crystalline structure . Many other intermediate and related structures are also known. [13] Most are produced from ores by a variety of wet processes using acid and base.