Lab 6 Quantitative Analysis.docx - Lab 6 Determination of...

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Lab 6: Determination of Water Hardness by EDTA Titration Dianie Fontenelle Team Members: Gina Whitten and Nelcy Ibarra Group #7 6 April, 2017
Purpose : Using an EDTA titration, students will measure the total concentration of Ca 2+ and Mg 2+ in water and determine the water hardness of a 15 mL unknown; reporting if the unknown is either “hard” or “soft.” Materials: 4mM Mg ̴̴ 2+ solution 0.01 M EDTA titration solution ̴̴ NH 3 /NH 4 + , pH 10 buffer Calmagite indicator 2400ppm CaCO 3 Stock solution Pipet 100mL volumetric flask Erlenmeyer flasks Beakers Buret pH paper Stirring rod Distilled water Procedures: 1. Prepare a working standard solution of 600 ppm CaCO 3 a. Prepare by pipetting 25mL of the 2400ppm solution into a 100mL volumetric flask. Dilute solution to the mark with distilled water and mix well. 2. Performing a blank concentration a. Add approximately 25 mL of distilled water into an Erlenmeyer flask. b. Pipet exactly 2mL of 4 mM Mg 2+ solution, add 12 drops of the calmagite indicator, and add enough NH 3 /NH 4 + until the pH of the solution is about 10 (test for a pH approximation of 10 using pH paper).

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