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Nernst Equation - DOC

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					Objective: In this experiment I will be using the Nernst equation to calculate potentials for cell at nonstandard conditions by measuring standard electrode potentials for several halfreaction. Formulas/Equations/Definitions: E0cell = E0ox + E0red Absolute potential of a single half-reaction cannot be measure. Relative potential of a particular half-reaction can be measured by coupling the halfreaction with the standard hydrogen electrode 2H+(aq) + 2e-  H2(g), E0red = 0.000 V @ 25oC 1 atm pressure Pb(s)  Pb2+(aq) + 2eNernst Equation Ered = E0red – 0.0592 / n * log Q Procedure:              Clean four copper, two lead, one zinc, and two silver electrodes by rubbing them lightly with sand paper Use a 50-ml beaker for each electrode solution Fill beaker about half full with the appropriate solutin To make identification easier, the lead, zinc, and silver solutions may contain food coloring Place the appropriate electrode in each solution Measure out 100 mL of 0.10 M KNO3 solution and pour it in a 400 mL beaker Heat the solution until starts to boil Remove the solution from the heat and slowly add 1 gram of agar to the hot solution, stirring constantly until all the agar dissolves Let the solution cool somewhat, but while still warm, pour it into a U-tube and insert cotton plugs as demonstrated by your instructor Cool the tube to room temperature, the mixture should form a gel Use fresh cotton plugs when changing cells to eliminate contamination Moisten the cotton plugs with the appropriate solutions before inserting them into the ends of the U-tube. Use your foreps Do not immerse the U-tube in the solution s to the level of the agar. Only the cotton plugs should touch the solutions. E0ox = +0.126 V


				
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Description: In this experiment I will be using the Nernst equation to calculate potentials for cell at nonstandard conditions by measuring standard electrode potentials for several half-reaction.