CHEMISTRY

CARBOHYDRATES  are naturally occurring organic compounds containing carbon, hydrogen and oxygen, with the hydrogen and oxygen present in the ratio of 2:1, as in water. The general molecular formula of carbohydrate is Cₓ(H₂O)ᵧ or CₓH₂ᵧOᵧ. Carbohydrates can be classified into simple sugars and complex sugars. Simple sugars are crystalline, soluble in water and have a sweet taste. Structurally, they can be further divided into monosaccharides, e.g. glucose, and disaccharides, e.g. sucrose. Classification of Carbohydrates Monosaccharides Monosaccharides are simple sugars with three to six carbon atoms per molecule. However, the most common and important of these are the ones containing six carbon atoms per molecule, the hexoses, e.g. glucose, fructose, galactose and mannose. All hexoses have the same molecular formula, C₆H₁₂O₆, but possess different spatial arrangements. Hexoses can exist both in the open chain and cyclic forms in solution. In so...

Phosphorus is a non-metallic element belonging to Group 15 and Period 3 of the periodic table. It is highly reactive and is never found in the free uncombined state in nature. Atomic Properties Chemical symbol: P Atomic number: 15 Relative atomic mass: 31 Electronic configuration: 1s² 2s² 2p⁶ 3s² 3p³ Oxidation states: −3, +3 and +5 Occurrence Phosphorus occurs naturally as phosphate rocks or phosphorite, primarily as calcium trioxophosphate(V), [Ca₃(PO₄)₂], and apatite, [Ca₅(PO₄)₃F]. It is also an essential component of living things, found mainly in bones and teeth as Ca₃(PO₄)₂. DNA, RNA and ATP contain phosphorus. Allotropes of Phosphorus Phosphorus exhibits allotropy, i.e. the existence of an element in two or more different physical forms in the same physical state. The three major allotropes of phosphorus are: 1. White phosphorus 2. Red phosphorus 3. Black phosphorus White Phosphorus 1. White phosphorus is a tetra-atomic molecule (P₄). 2. Each phosphorus atom undergoes...

SILICON Silicon is a metalloid which belongs to the same group in the Periodic Table as carbon. It does not occur free in nature but is found mainly in the combined form as: I. Silicon(IV) oxide, SiO₂, and  II. Trioxosilicates(IV). Silicon is the second most abundant element in the Earth's crust after oxygen. Naturally occurring silicon compounds exist mainly as: I. Silicon(IV) oxide, SiO₂ II. Metallic trioxosilicates(IV) Silicon(IV) oxide is commonly called silica . It occurs in crystalline forms such as: I. Quartz II. Flint III. Opal IV. Horn-stone V. Jasper It is also the main constituent of: I. Sand II. Kieselguhr Metallic trioxosilicates(IV) occur in rocks such as: I. Granite II. Basalt Clay and kaolin consist mainly of hydrated aluminium trioxosilicate(IV).   PREPARATION OF SILICON A. Amorphous silicon Amorphous silicon can be prepared by heating a mixture of pure dry sand and magnesium powder in a fire-clay crucible. Dilute hydrochloric acid is then added ...