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Unformatted text preview: Buret Preparation and Calibration Zhihua Shi TA: Annette Medina-Morales Chem 100A Section A05 NSB 2311, UC San Diego January 24, 2008 Abstract This experiment helped students to learn the proper usage of many precision instruments such as buret, eppendorf pipet helper, and pipet pumps. Deionized water was used in this experiment and two values were determined-- volume /drop and drop/volume. There are approximately 16.90 drops in 1 mL of water. However the highest frequency of data is around 19 drops. This error could have resulted from the random error. Furthermore, the volume per drop of water was determined to be approximately 0.059 mL. All the results are very close expected for one. This value turned out to be an outlier because a Q-test was not performed during the experiment. The second part of the experiment was to learn how to calibrate instruments. Instruments need to be calibrated periodically in order to determine the tolerance of that instrument. The tolerance of a buret was determined to be 0.069 mL, very close to the value indicated in the Tolerances for NBS Precision Grade Glassware table. 1. Introduction Many laboratory experiments require the use of various instruments. Some of the instruments give precise measurements and some only give rough estimates. Precise measuring instruments such as burets, pipets, and volumetric flasks are very helpful in performing many of the experiments in Chem 100A. Therefore it is important to know the proper usage of these instruments. No matter how precise an instrument can be, there will always be some indeterminate error. Therefore the goal of this experiment is to demonstrate the proper usage of instruments such as buret and eppendorf pipet helper to minimize determinate errors. Two things can be determined by using a buretthe volume of solution in buret and drops of solution removed from a buret. The two numbers are plotted on a graph that can be very helpful during other experiments. Furthermore, many micropipettes must be calibrated periodically to determine the error or correction, which in turn gives more accurate measurements. In this experiment, water removed from a buret is weighed on an analytical balance. The temperature of water is measured and the correction and percentage error are determined. Since only water is used in this experiment, chemical species and reactions are not available. 2. Experimental 2.1 Materials and Reagents Deionized water was first allowed to become surrounding temperature. It was then used to determine the ratio of volume and drops in water. A buret was used to measure the volume of water. Buret Calibration and practice of Eppendorf pipet helper and pipet pumps were done by using deionized water as well. No chemicals were used in this experiment....
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- Winter '06