Saturday, August 17, 2019

Lab Report of the Preparation of Cds

EXPERIMENT REPORT (PREPARATION OF CdS) Experiment Purposes 1. To master the proper operations as well as the suitable situations of atmospheric pressure filtration, vacuum filtration, centrifugal separation & precipitation washing 2. To understand the relation between precipitation state % precipitating conditions 3. To learn the way to examine whether reactants are fully precipitated 4. To learn the principals of powder material synthesizing through room temperature solid phase method & liquid phase method directional growing rystal form of precipitation Experiment Principals 1. the process of precipitation forming constitutive crystal ion accumulating growing forming nuclei sediment particals amorphous precipitation crystal nuclei 2. the classification of precipitations amorphous precipitation, particle diameter smaller than 0. 02 m, ex. Fe(OH)3. the hydroxide of metals of high oxidation number would grow directionally with low rate, but accumulate very fast, forming amorphous prec ipitation curd-like precipitation, particle diameter 0. 02~0. 1 m, ex.AgCl crystal form of precipitation, diameter 0. 1~1 m, ex. BaSO4. Inorganic salts with strong polarizability grow directionally with high rate, forming crystal form of precipitation 3. CdS is a semiconductor material widely use. It can be preparated through room temperature solid phase method & liquid phase method & gas phase method. Use CdSO4 and NaS as reactants, through both room temperature solid phase method & liquid phase method to prepare CdS(s). Compare the two ways of preparation and their influence on product separation. Reactions as ollows, CdSO4+2NaS=CdS+Na2SO4 Chemical reagents: CdSO4(s), Na2S(s), 0. 3M HCL(aq), 0. 5M CdSO4(aq), 1M BaCl2(aq), widely pH tests strips, mortar, centrifugal text tube, bake oven, centrifuge, vacuum filtration apparatus, etc. Experiment Steps And Phenomena Room temperature solid phase method 1. according to the theoretically volume of product should be 1. 44g, weigh certain amount of CdSO4(s) and NaS(s), mix in dried mortal, then grind for 10-20 min. | In the mortal, White particles slowly turned into orange powders, bad egg smell is output. | 2. he product is transferred to a beaker and washed with distilled water for 3 times, until the supernatant is tested pH

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