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Title: Preparation And Studies of Potassium Diaquabis(Oxalato) Chromate (III) Dihydrate {K[Cr (C2O4)2(H2O)2].2H2O}Objective:To prepare potassium diaquabis(oxalate) chromate (III) dihydrate complexes and study its reactions. Introduction:Chromium (Cr) is found in group 6 (VIB) of the Periodic Table along withmolybdenum (Mo) and tungsten (W). It is located at Period 4 and has atomic number of 24.These metals, therefore, have 6 valence electrons. In the chromium atom, the 3d-orbital ishalf-filled with 5 electrons and 6thelectron is present in 3s orbital. It is in solid state at roomtemperature and density of 7194 kgm -3. Electron configuration of chromium is [Ar] 3d54s1.Boiling point and melting point of chromium are 2671oC and 1907 oCrespectively. Besides,it has atomic mass of 51.9961 amu. This transition metal is a lustrous steel-gray color whichtakes a high polish. It is hard and resistant to corrosion. Chromium has a high melting point,stable crystalline structure, and moderate thermal expansion. All chromium compounds arecolored. Chromium compounds are toxic. Chromium is used to harden steel. It is acomponent of stainless steel and many other alloys. The metal is commonly used for platingto produce a shiny, hard surface that is resistant to corrosion. Chromium is used as a catalyst.It is added to glass to produce an emerald green color. Chromium compounds are importantas pigments, mordants, and oxidizing agents.The principal ore of chromium is chromite(FeCr2O4). The metal may be produced by reducing its oxide with aluminum.It can be useddirectly for the manufacture of steel and other chromium compounds. An alloy of chromiumand nickel, nichrome is used for electrical heating elements.Chromium (III) compounds aresparingly soluble in water.Chromium (III), the most stable oxidation state of chromium, forms a number ofcomplexes, in which six monodentate ligands surround the cation octahedrally. The colors ofthese complexes are determined by the ligands attached to the Cr centre. In the abovecompound, two oxalate anions (bidentate ligands) and two water molecules coordinate thechromium cation to provide oxygen atoms at the corners of the octahedron. Two geometricalisomers exist for the complex ion, [Cr(C2O4)2(H2O)2]-, two (C2O4)2-ions [or two H2O
molecules] can be on the same side of octahedron structure of the complex ion giving the cisisomer or on the opposite sides giving transisomer.Preparation (1)A pestle and mortar were used to powder 0.0555 mole oxalic acid dihydrate andseparately 0.0068 mole K2Cr2O7. The powders were mixed thoroughly, regrindingthem gently.(2)The mixture was transferred into a 100 ml beaker. The beaker was covered with asmall watch glass and heated gently the beaker on the hot-plate. A vigorous reactioncommenced with the evolution of steam and carbon dioxide and with the formationof a dark semi-solid compound.

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