Experiment 1 - Gravimetrics

Experiment 1 - Gravimetrics - CHEM 257 Experiment 1...

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CHEM 257 Experiment 1 Check-in; Weighing, Density, Uncertainty, Bimodal Distributions, Reduction Potentials Before coming to the laboratory: Carefully read the sections in the document “ General Information Chemistry 257 ” entitled Laboratory Safety Regulations ” and “ Safety in the Laboratory ”. This must be done before coming to the first laboratory section meeting . Before beginning any laboratory work, you have to read these sections and be familiar with their contents and then sign the form indicating that you have done this. Come to the laboratory in Room 80 HA at 1:10PM for your section starting Monday, September 13, 2010. The first day in the laboratory: 1. Turn in your signed statement that you are familiar with laboratory safety precautions and rules. Get your locker assignment and lock combination from the teaching assistant. Open your locker and inspect the items to make sure that everything is present and in good condition. Dirty, broken, chipped or missing items will be replaced free at check-in time; thereafter you are responsible and may be charged for replacement items. A diagram is provided that illustrates most of the equipment. It is easiest to remove all equipment and check the list as you put the apparatus in the locker. If you have any questions about any piece of apparatus, ask. Keep the equipment list in your locker until end-of-the-semester check-out. Half of the section will check in, while the other half carries out the following experiments. 2 . Copy the data sheet into your notebook before beginning the laboratory. After the teaching assistant has explained how to operate the top loading (measure mass to a reported value of 0.01g) and an analytical balance (in the room off the adjoining laboratory, measure mass to a recordable value of 0.0001 g that is 1/10 th of a milligram), determine the replication error of an analytical balance by measuring the mass of the SAME penny 10 times. With gloves, take it off, retare the balance and remeasure each time. Determine the mean mass of that penny and the sample standard deviation of it. Just for fun, place that penny on the balance using slightly wet fingers. How much does a wet finger print weigh? You will then be given a collection of 20 pennies. Weigh each of the 20 pennies on a top loader balance. The reason you can use this less accurate balance is that pennies in circulation will have a standard deviation that is 100 times greater than the measurements of a single penny 10 times. For each penny, record the date on the penny then tare the balance and then place the penny on the balance and record the mass. In the interest of time, tare the balance with the first penny on it and record the date and mass of the 2 nd penny, etc. Place the pennies that weigh approximately 2.5g in one pile and those close to 3.0g in another pile (on the balance). The result of these experiments will be a set of 20 measurements of mass and date and the 2 sets will be separate. Enter your data on the report form.
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Experiment 1 - Gravimetrics - CHEM 257 Experiment 1...

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