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Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula SiO 2, commonly found in nature as quartz. [5] [6] In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant families of materials, existing as a compound of several minerals and as a
W-silica is an unstable low-density form involving SiO tetrahedra sharing opposite edges instead of corners, forming parallel chains similarly to silicon disulfide (SiS 2) and silicon diselenide (SiSe 2): it quickly returns to forming amorphous silica with heat or traces of water. [14] Condensed polysilicic acid. Silica is rather inert chemically.
Silicates with alkali cations and small or chain-like anions, such as sodium ortho-and metasilicate, are fairly soluble in water. They form several solid hydrates when crystallized from solution. Soluble sodium silicates and mixtures thereof, known as waterglass are important industrial and household chemicals. Silicates of non-alkali cations ...
[4] [5] [6] Dehydrating the latter yields a hard translucent form of silica with atomic-scale pores, called silica gel, which is widely used as water absorbent and drying agent. Silica dissolves very sparingly in water [citation needed] and is present in seawater at concentrations below 100 parts per million. In such dilute solutions, silica is ...
In mineralogy, silica (silicon dioxide, SiO 2) is usually considered a silicate mineral rather than an oxide mineral. Silica is found in nature as the mineral quartz , and its polymorphs . On Earth, a wide variety of silicate minerals occur in an even wider range of combinations as a result of the processes that have been forming and re-working ...
Dissolved silica (DSi) is a term used in the field of oceanography to describe the form of water-soluble silica, which is assumed to be Si(OH) 4 (orthosilicic acid) or its conjugate bases (orthosilicate anions) such as − O−Si(OH) 3 and (− O−) 2 Si(OH) 2.
Silica gel is an amorphous and porous form of silicon dioxide (silica), consisting of an irregular tridimensional framework of alternating silicon and oxygen atoms with nanometer-scale voids and pores. The voids may contain water or some other liquids, or may be filled by gas or vacuum. In the last case, the material is properly called silica ...
Like other chlorosilanes or silanes, silicon tetrachloride reacts readily with water: . SiCl 4 + 2 H 2 O → SiO 2 + 4 HCl. The reaction can be noticed on exposure of the liquid to air, as SiCl 4 vapour produces fumes as it reacts with moisture to give a cloud-like aerosol of silica and hydrochloric acid. [6]