In the lower concentration half cell the

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magnitude lower. In the lower concentration half-cell, the concentration will be limited by the solubility product of an insoluble copper salt. The half-cell potential for each half-cell will be ܧ ൌ 0.337 െ ோ் ଶி ݈݊ ሾ஼௨ మశ (13) The half-cell with the higher concentration of Cu 2+ will have the larger reduction potential, so it will be the cathode. As a result, for this special case, ∆ܧ ൌ െ ோ் ଶி ݈݊ ቀ ሾ஼௨ మశ ೌ೙೚೏೐ ሾ஼௨ మశ ೎ೌ೟೓೚೏೐ (14) since ∆E o = 0 because the standard reduction potentials cancel. S AFETY Using safe laboratory practices is important when using unknowns. Some of the metal salts are toxic. Lead nitrate, for example, is a poison. Others, such as aluminum chloride and silver nitrate, are corrosive. Silver nitrate will also turn your skin black after it is exposed to light. Always wear gloves and goggles. Keep the chemicals under the hood and work with your face as far from the chemicals as possible. E XPERIMENTAL P ROCEDURE You will have one lab period to complete all three parts of this experiment. Obtain a reaction plate with 6 wells, a multimeter, 2 alligator clips, and a glass thermometer from the stockroom along with two copper metal strips and one lead metal strip. You will also need a 20-ml volumetric flask, a 100-ml volumetric flask, and a 1-ml pipette and pipettor. Your TA will give you short pieces of string to use as salt bridges in Parts A and B and a strip of filter paper to use as the salt bridge in Part C. Part A: Construct a lead-copper galvanic cell. You will need to prepare two solutions: CuSO 4 ~0.05M 100 ml quantity Pb(NO 3 ) 2 ~0.05M 20 ml quantity Determine the amounts of chemical you will need to make these solutions. Your final concentration should be within 10% of these concentrations. The copper (II) sulfate salt is hydrated, with the molecular formula CuSO 4 5H 2 O. The lead nitrate salt is not hydrated. Check your calculations with your lab partner and answer the first question on the in-lab worksheet before making the solutions. Note: To avoid long lines at the balances, you should only get one salt at a time. Make up the first solution before getting the second salt. By then, the lines will be gone. Students who monopolize the balances before everyone has had a chance to get at least one of the compounds will lose points. Use the following procedure to fill volumetric flasks when you need to dissolve a compound and accurately know the concentration. A video showing this technique is on Blackboard. You will be tested individually on making solutions as part of the lab skills exercise later this semester. 1) Dissolve the measured amount of compound in a beaker, using about 50% of the volume of the volumetric flask. So, for example, you should dissolve the copper(II) sulfate in about 50 ml of water in a beaker. Also rinse any solid remaining in the weighing pan into the beaker using your wash bottle. Then pour that into the volumetric flask.

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