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Unformatted text preview: Fall 2007 Chemistry 300 Cornell University Lab 1 Check in, Clean Glassware, and Calibrate Volumetric Pipettes I. INTRODUCTION In this one-week lab you will verify that your desk has all the equipment necessary for the semesters ex- periments. You will then clean the equipment in your desk. In subsequent labs you will be measuring concen- trations of chemicals down to levels of parts per million. In order to obtain such accuracy it is crucially important that your glassware is clean. During this first lab period you will also calibrate your desks volumetric pipettes. These pipettes, along with your desks volumetric flasks and the shared analytical balances, will be your workhorse instruments this term. If the volumetric pipettes are well cleaned and properly read, they will allow you to dispense an amount of liquid that is known to nearly three decimal places. II. MATERIALS AND METHODS You will need Five volumetric pipettes: 1ml, 2ml, 5ml, 10ml and 25 ml Blue pipette bulb Thermometer Distilled water Analytical balance The goals of todays experiments are to determine the precision and accuracy of your pipettes. You will ac- complish this by discharging water from a pipette into a beaker on a tared balance. Because the density of wa- ter is very well known, you can determine the volume delivered from the mass. Before coming to lab, you should read the following sections from Harveys text: 2D.1 (measuring mass), 2D.2 (measuring volume), 4A.1 (mean), 4A.2 (standard deviation), 4B.1 (accuracy), and 4B.2 (precision). At the beginning of the lab period your TA will demon- strate how to 1. draw solution into a volumetric pipette, 2. dispense solution from a volumetric pipette, and 3. clean a volumetric pipette. III. WASTE N/A. IV. PROCEDURES A. Equipment Check Obtain a list of equipment from your teaching assis- tant. Make sure that your desk has all the equipment listed. If it does not, contact your TA to obtain the missing equipment. You may obtain 1 mL and 2 mL vol- umetric pipettes from the front of the room. You may keep them in your desk for the rest of the term....
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- Fall '07