68thandZinc - Annya Valderrama CHEM 106-02 October 25, 2011...

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Unformatted text preview: Annya Valderrama CHEM 106-02 October 25, 2011 Lab: 68 th & Zinc I. Introduction: The purpose of this experiment is to find out how one quantity can be logically deduced from the other know variable in an elegant sequence of steps, as well as learn fundamental techniques what chemist call “wet chemistry”. Zinc ion forms a stable water-soluble 1:1 complex with EDTA, which is the basis for the determination of Zn in this experiment. EDTA titrant and a standard Zn2+ solution are prepared. The EDTA solution is standardized by titration of aliquots of the standard zinc solution. The titration is carried out at pH 10 and uses the Eriochrome Black T indicator which changes color from “purple” to “pure blue” at the endpoint. II. Focus Questions: 1. What is the percent zinc of the zinc iodide product as determined by a Titrimetric analysis? 21.10% 2. 2.) What is the Percent Zinc of the Unknown Zinc Salt as Determined by a Titrimetric analysis? 38.41% III. Substance Used: • Zinc Iodide – white powder form • Na 2 H 2 EDTA(s)- • Unknown Zinc Compound – White granular form • 6M Acetic Acid –clear liquid • pH10 buffer solution – clear liquid • calamagite indicator solution – brown to black liquid IV. RAW DATA Reacting EDTA with Zinc ion in Zinc Iodide Trial Mass of ZnI 2 Initial EDTA 4- Final EDTA 4- 1 0.25 g 47.001 mL 24.501 mL 2 0.25 g 43.998 mL 28.400 mL 3 0.25 g 49.800 mL 25.100 mL V. Calculations: Concentration of EDTA 4- Na 2 H 2 EDTA (s) + H 2 O (l) EDTA 4- (aq) + 2Na + (aq) + 2H + (aq) 3.65 g EDTA x 1 mol / 372.24 g/mol = .0098 g/mol Volume = 250 mL 0.250 mL Molarity = .0098mL/0.25 L = 0.0392 M Total volume of EDTA 4- titrated Initial Volume – Final Volume = Total volume titrated Trial #1 47.001 mL – 24.501 mL = 22.500 mL Trial #2 43.998 mL - 28.400 mL = 15.598 mL Trial #3 49.800 mL – 25.100 mL = 24.700 mL Moles of zinc cation reacted at end point Trial #1 .0392 M EDTA 4- x 0.0225 L = 8.82e-4 M of EDTA 4- reacted Trial #2 .0392 M EDTA 4- x 0.0284 = .00111328 M of EDTA 4-...
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This note was uploaded on 11/17/2011 for the course CHEM 106 taught by Professor Bachu during the Fall '10 term at CUNY Hunter.

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68thandZinc - Annya Valderrama CHEM 106-02 October 25, 2011...

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