Volumetric Analysis

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Determining the Amount of a Substance and its Composition Using Volumetric Analysis. Amy Gerber INSTRUCTOR: Alisha Etheredge 11/25/2014 PURPOSE/INTRODUCTION This experiment shows the method for determining the amount of a substance when volumetric analysis is used. Volumetric analysis uses the volume of a reactant used with the substance to determine the amount of the substance. In this case, an unknown chloride salt (XCl) will react with silver nitrate (AgNO3) to create the precipitate, silver chloride (AgCl). By recording the amount of silver nitrate (AgNO3) is used, the amount of the chloride used is figured. An indicator is used to help determine when the reaction is complete. The indicator used in this experiment is potassium chromate (K2CrO4). The recorded volume of silver nitrate (AgNO3) used is then used to determine the molarity of the silver chloride (AgCl) created. Moles of AgCl = (Volume of AgNO3 added) × (Molarity of AgNO3) Using the molarity of the silver chloride (AgCl) and the atomic weight of the chloride (35.4527), the weight of the chloride from the original unknown chloride salt sample. Weight of Cl- in XCl sample = (moles of AgCl) × (atomic weight of Cl- = 35.4527) The amount of chloride as a percent of the original unknown chloride salt is figured using the weight of the chloride divided by the weight of the original sample, then multiplied by 100. % Cl- in sample = (weight of Cl- in XCl sample / weight of XCl sample) × 100 % This experiment is performed three (3) times to average the volume of silver nitrate (AgNO3) used. Average volume of AgNO3 = (volume AgCl #1 + volume AgCl #2 + volume AgCl #3) / 3 The hypothesis in this experiment is that the amount of the first reactant can be determined from the volume of a second reactant needed to complete the experiment. MATERIALS Materials required to perform this lab