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Mitchell Graded Exp 5

Mitchell Graded Exp 5 - Experiment 5 Conductometric...

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Experiment 5 – Conductometric Titration Spring 2008 Name Lab Day and Time TA Section Documentation Grading Rubric Possible Points Points Received Introduction 10 Purpose of report Goals of the experiment Materials and Methods 20 Describe procedure in paragraph format following guidelines provided (-2 for each type of mistake) Results and Discussion 50 Inserted titles for tables Inserted graphs into template Inserted captions for each graph Showed complete sample calculations Summarized all data in tables Answered questions completely Error analysis Laboratory Technique 20 TOTAL (100) 83 TA Comments/Suggestions:
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C HEMISTRY 11L R EPORT T EMPLATE EXPT. Conductometric Titration 5 Introduction The purpose of this report is to determine the empirical formula of calcium phosphate and to compare the chemical equations of the theoretical value, the class experimental value, and the current study’s experimental value. The objective of the experiment was to use a conductometric titration to measure the volume and conductivity of phosphoric acid to determine the number of moles of phosphate ions. Materials and Methods The procedure for this experiment was taken from the University of North Carolina at Chapel Hill Chemistry 101 Lab Manual. There were no deviations from the given procedure. For the gross trial, the dried calcium hydroxide was obtained from the desiccator. The cap was placed on the weighing bottle. To ensure the sample remained anhydrous, the cap was left on as much as possible. The mass of the weighing bottle containing the calcium hydroxide sample was determined on the balance, and the mass was recorded. About 0.05 grams of the calcium hydroxide sample was gently tapped out of the weighing bottle into a 250-mL volumetric flask. The weighing bottle was reweighed after the transfer on the same balance. The difference between the mass determined before and after transfer provided a more accurate measure of the mass transferred to the 250-mL volumetric flask. The mass of the calcium hydroxide sample transferred was determined. After ensuring that the mass of the calcium hydroxide sample was between 0.04 and 0.06 grams, the exact mass was recorded (0.054 grams). The base of the 250-mL volumetric flask was about halfway filled with distilled water. The solution became cloudy. The flask was swirled and inverted for 5 minutes to dissolve the solid. Distilled water was carefully added to the fill line of the 250-mL volumetric flask. The solution was inverted and swirled ten times. Fifty milliliters of calcium hydroxide solution was transferred into a 100-mL beaker using a 25-mL volumetric pipet. A buret was filled with the phosphoric acid solution, and the exact molarity was recorded (0.01638 M). Using a three-prong clamp, the conductivity sensor was positioned in the calcium hydroxide solution, away from the stir bar. The run was started on Data Studio, and an initial reading was taken before adding any titrant. KEEP was pressed to record the conductivity of the solution and the corresponding volume measurement of 0.00 mL was entered into the dialog box. Phosphoric acid was
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