1-3 Guide - CHEM 6BL Experiments 1-3 Guide EXPERIMENT 1...

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CHEM 6BL Experiments 1-3 Guide Page 1 of 10 EXPERIMENT 1 GUIDE Gravimetric Analysis In this experiment, students precipitate the Al 3+ ion in a solution of unknown concentration by reacting it with an organic anion, 8-hydroxyquinolinate, forming a solid complex of aluminum known as aluminum 8-hydroxyquinolinate. From the stoichiometry of the reaction, the exact mass of precipitate obtained and the volume of solution used, students determine the aluminum concentration in their unknown sample. This guide contains a list of expected learning outcomes, laboratory procedures & laboratory report hints, and some of the common lab-specific questions often asked by students in this course. The identity of the author(s) of any new questions posted will remain anonymous. However, I reserve the right to modify any of the questions in order to provide clarity to the reader. EXPECTED LEARNING OUTCOMES Upon successful completion of this experiment, you should be able to: Operate an analytical balance correctly (including calibration and taring) Operate a Bunsen burner correctly Use proper technique with a volumetric pipet Use proper technique for vacuum filtration Understand and apply the principles of desiccation Execute the steps involved in the formation, digestion, and washing of a precipitate Apply the principles of stoichiometry to gravimetric analysis and the calculation of the concentration of an analyte solution Assess the precision of the data collected and perform an error analysis accurately Write an organized formal laboratory report reflecting the student’s ability to analyze data and draw conclusions
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CHEM 6BL Experiments 1-3 Guide Page 2 of 10 LAB PROCEDURE Be sure you write down your Unknown Solution ID # . You will need this information to ID your unknown concentration in your Abstract , Results & Discussion . In this experiment, one of the common problems is to obtain too little or too much precipitate , leading to a calculated concentration of [Al 3+ ] that is either too low or too high ! Be sure that you have precipitated ALL of your possible Al(Ox) 3 (aka. Alq 3 ) and that you have done the experimental procedure correctly so that you will generate the maximum amount of precipitate. Also make sure you have fully dried your precipitate products in order to avoid overestimating [Al 3+ ]. It is now believed that the most likely causes for obtaining too little or too much precipitate are: 1) the p H is still out of balance (e.g., too little acetate buffer has been added), so CHECK YOUR p H and add more buffer if necessary, or 2) your product is still wet , so make certain you have fully dried your product! LAB REPORT
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1-3 Guide - CHEM 6BL Experiments 1-3 Guide EXPERIMENT 1...

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