F pour the agar solution into each of the crucibles

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f) Pour the agar solution into each of the crucibles at your lab station until you have about 7 – 8 mm of agar solution in each crucible. (Use tongs – palm up!) As the agar solutions cool, a gel should form. This will take 15 to 25 minutes (setting the crucibles and beaker on ice will accelerate gel formation). After the gel has formed, the salt bridges for the various experiments are ready. Avoid punching holes through the gel’s surface with the electrode. This lab is divided into two Sections. One half of the lab will do Parts A1 to A4 experiments during week 1, and one-half of the lab will perform Part B during week 1. In week 2, students reverse assignments so that all students complete all experiments.
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Chemistry 132 Lab Manual Page 45 Part A1. Cell potentials The following five electrode systems are to be studied: Ag + /Ag(s) single yellow band on Ag electrode Cu 2+ /Cu(s) no band on Cu electrode Zn 2+ /Zn(s) single red band on Zn electrode Fe 3+ / Fe +2 /Pt(s) two white bands on Pt electrode a) Dispense approximately 50 mL of 0.05 M silver nitrate solution (AgNO 3 ) into a 100 x 50 mm crystallizing dish. The volume is not critical. b) Carefully transfer 5 mL of 0.05 M Cu 2+ solution to a crucible containing agar. 5 mL of 0.05 M Zn 2+ solution to a second crucible containing agar. 5 mL of 0.05 M Fe 3+ / Fe +2 solution to a third crucible containing agar. Use masking tape to label the solution in each crucible. Place the crucibles into the 100 x 50 mm crystallizing dish. Be sure you do not trap large air bubbles under any of the crucibles. After you add the crucibles to the crystallizing dish, tape a silver electrode to the side of the dish with 3-4 mm of the silver wire in the silver nitrate solution. c) Record in your notebook the solute ion concentrations used, together with the electrode used in each of these solutions. A silver electrode is placed in the silver nitrate solution (Ag + ), a copper electrode is used with the Cu 2+ solution, a platinum electrode with the Fe 3+ / Fe +2 solution, and a zinc electrode is used with the Zn 2+ solution. d) Use the digital voltmeter on the 2 V full-scale setting to measure the cell potentials (various combinations of half-cells) relative to the Ag + /Ag(s) half-cell we choose as our “standard” half-cell. Make these measurements by attaching the copper end of the silver electrode to the black alligator clip, which is connected to the digital voltmeter at the COM (also called the neutral, ground, or negative) input. Be sure you have good contact between the alligator clip and the copper part of each electrode. Attach the copper end of one of the other electrodes to the red alligator clip and hold this electrode in its corresponding solution. You need only 3-4 mm of the electrode in the solution to obtain a reliable voltage. The electrode in the solution in the crucible should remain above the surface of the agar. Record the voltage. In addition to the voltage, your notebook should include how each electrode is connected to the digital voltmeter (COM is the negative input).
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Chemistry 132 Lab Manual Page 46 Including drawings in your notebook may help.
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