Essay on Chem Lab Report

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Synthesis Procedure 1
-1.0 Introduction A Cobalt-Amine-Halide compound is synthesized from cobalt (II) chloride hexahydrate. An orange-tinted solid is produced and is considered to be unknown since the specific ligand amounts are unknown. By determining the percent composition of various elements and compounds in the unknown, its true identity can be predicted. Chloride, ammonia, and cobalt are three examples of percent compositions determined to help narrow the selection of possible unknowns. Titrations using Na2S2O3 and HCl to determine percent cobalt and ammonia, respectively, are used. Silver nitrate is used to precipitate the chloride ions in the unknown, which can be measured to determine the percent composition of chloride
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KIO3 is added to an HCl and KI solution containing excess KI and I- ions. KIO3 acts as a primary standard and reacts to produce I2, which can then be reacted with the Na2S2O3. The yellow/brown color during the triplicate titrations is due to the presence of I3-. Starch indicator is added to the slightly titrated yellow-colored solution to help easily see the endpoint. The liberated I2 needed about 31.49mL of Na2S2O3 solution during the titration to reach the endpoint. The molarity of Na2S2O3 used for the titration is found to be .10270M with .159% deviation (Table 5).
IO3- + 6 H+ + 5 I-  3 I2 +3 H2O
6 S2O32- + 3 I2  3 S4O62- + 6 I-

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