![]() SILICATES - PRACTICE MCQ QUESTIONS & ANSWERS CSIR NET GATE IIT JAM JEE NEET * The basic silicate minerals readily react with weak acids and undergo * With increase in the degree of polymerization, there is decrease in theĬharge per silicon atom as well as the basicity of silicate mineral. While for tecto silicates (most polymerized silicate) = 2:1. The values of O/Si for ortho silicates (lease polymerized) = 4:1 Greater the degree of polymerization, lower will be the O/Si * The degree of polymerization is denoted by Oxygen to Silicon * Silicate minerals are very common in the Earth crust since Oxygen and Feldspar, Zeolites, Ult etc., A FEW IMPORTANT POINTS ABOUT SILICATES When SiO 4 4- units are replaced by AlO 4 5- units, three dimensional aluminosilicates are formed.Į.g. SiO 2 - Quartz, Tridymite and Crystobalite - These are the crystalline forms of silica. All the oxygen atoms of SiO 4 are shared with other tetrahedra and thus by forming three-dimensional network.Į.g. The general formula of three dimensional (3-D) or tecto or Framework silicates is (SiO 2) n. Muscovite mica - KAl 2(AlSi 3O 10)(F,OH) 2 -Īnd Lepidolite - KLi 2Al(Al,Si) 3O 10(F,OH) 2ģ) Clay : It is an aluminosilicate with sheet structure.ħ) THREE DIMENSIONAL SILICATES (TECTO SILICATES) Is the softest material with a smooth and greasy touch.Ģ) Micas : General formula is X 2Y 4–6Z 8O 20(OH,F) 4Į.g. ![]() Layers are held together by weak van der Waal's forces.ġ) Talc - Mg 3Si 4O 10(OH) 2 : It is the main ingredient of soap stone. It These silicates can be cleaved easily just like graphite. The Each SiO 4 tetrahedron shares three oxygen atoms with others and thus by forming two-dimensional sheets. Two dimensional (2-D) silicates is (Si 2O 5) n 2n. The general formula of Sheet or Phyllo or Note: The single and double chain silicates are collectively known as Hence their applications are restricted nowadays.Ģ) Tremolite - Ca 2Mg 5(Si 4O 11) 2(OH) 2 These are carcinogenic amphiboles affecting the lungs. They have been used for thermal insulation material, brake linings, construction material and filters. There are two types of tetrahedra: those sharing 3 vertices and those sharing only 2 vertices.ġ) Asbestos - These are noncombustible fibrous silicates. The general formula of double chain silicates (or Amphiboles) is (Si 4O 11) n 6n. Note: The formula of cyclic silicates as well as chain silicates is a pyroxene mineral consisting of lithium aluminium inosilicate Each unit shares two oxygen atoms with other units. 4) CHAIN SILICATES (PYROXENES)Ĭhain silicates or pyroxenes contain (SiO 3) n 2n- ions which are formed by linking ‘n’ number of tetrahedral SiO 4 4- units linearly. Well-known varieties of beryl include emerald andĪquamarine. Each aluminium is surrounded by 6 oxygen atoms Each unit shares two oxygen atoms with other units.ġ) Benitoite - BaTi(SiO 3) 3 : containing three tetrahedra arranged cyclicallyĢ) Beryl - Be 3Al 2(SiO 3) 6 : containing six-silicate rings Mineral in nature containing pyrosilicate ion.Ĭyclic silicates contain (SiO 3) n 2n- ions which are formed by linking three or more tetrahedral SiO 4 4- units cyclically. The pyrosilicate ion is less basic than orthosilicate ion. Structure of pyrosilicate is shown below. Pyro silicate (or Soro silicate or disilicate) contain Si 2O 7 6- ions which are formed by joining two tetrahedral SiO 4 4- which share one oxygen atom at one corner (one oxygen is removed while joining). The cations are octahedrally coordinated to the oxygen atoms of the silicate. Note: The Be 2+ and Zn 2+ ions are tetrahedrally surrounded by the oxygen atoms of silicate. Highly fluorescent (green) under shortwate UV. ![]() Silicate minerals are rare and only found with cations which form highlyġ) Phenacite (also known as phenakite) - Be 2SiO 4 The ortho silicate ion is the strong conjugate base of weak orthosilicic acidĪs well as it will not persist in aqueous solutions. Unit of ortho silicate unit is shown below. Ortho silicates (or Neso or Island silicates) are the simplest silicates which contain discrete SiO 4 4- tetrahedral units. The Three dimensional (or tecto) silicates 1) ORTHO SILICATES.Depending on the way the tetrahedral units are linked, the silicates are classified into the following types. Silicates are the minerals containing silicon and oxygen in tetrahedral SiO 4 4- units, which are linked together in several patterns. Practice questions What are Silicates? Formula.?.Types & Classification of silicates with.
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