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Effect of Concentration on Electrochemical Cell Potential Using Nernst Equation

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Mr. Idris IB Chemistry 14th October 2012 Effect of Concentration on Cell Potential Using Nernst Equation Introduction: Galvanic or voltaic cells convert chemical energy generated from the electron transfer in redox equations to electrical energy. The cell is composed of two half-cells. Each half cell has a metal electrode (the anode and cathode) and a solution of a salt of the same metal. In the anode the metal oxidizes and produces cations, while the cathode the cations in the solution are reduced and collect at the electrode. The circuit is connected with wires attached to each electrode so that there is a flow of electrons from the anode to the cathode. The half cells are connected with a salt bridge, usually potassium nitrate to allow the flow of anions from the cathode into the anode to balance the flow of electrons. Cell potentials (measure of the energy per unit which is available from the redox reactions) of the electrodes can be measured using the voltmeter. A standard electrode cell potential can be determined using galvanic cells under standard conditions which include 1 mol for each solution. ...read more.


U-shaped Plastic Tube Filter Paper Distilled water 20 ml Voltmeter with overhead LCD display and leads with alligator clips Copper and Zinc metal strips 1 M Copper nitrate {Cu(NO3)2} 50 ml 1 M Zinc nitrate {Zn(NO3)2} 50 ml Potassium Nitrate (KNO3) 100 ml Procedure: One end of the tube was stuffed with filter paper. Potassium Nitrate was put into the tube until no bubbles were present and the other end was stopped with filter paper as well, making the salt bridge. One beaker was filled 10 ml with copper nitrate and another beaker was filled with 10 ml zinc nitrate. An end of the salt bridge was placed into each beaker. The strip of copper metal was placed into the beaker with the copper nitrate solution and the strip zinc was placed in the beaker containing zinc nitrate. Clips connected to the voltmeter were connected to each metal strip. The voltage of the cells was then recorded by the voltmeter. Then each solution was diluted by adding 10 ml distilled water into each beaker. The same procedure of recording the voltage was used. ...read more.


(V) 1 1.00 0.99 1.01 2 0.50 0.92 1.01 Conclusion The data shows that the cell potentials are equal regardless of the concentration. This occurred because the concentrations of both solutions in the sets resulted in a reaction quotient of 0. So the effect of concentration on cell potential may not be observed and hence the hypothesis may not be supported. Evaluation A systematic error that occurred was that the voltmeter used to measure the voltage of the electrodes was not very sensitive which might have affected the electrode cell potential. A random error that occurred was that during the experiment an air conditioner was running which would have affected the experiment's surrounding temperature which would not have been constants. Improvements In order to make the experiment better, the concentration of only one of the solutions should be changed at a time to determine the effect of concentrations on electrode cell potential. Also to decrease the random errors the air conditioner should be turned off or the experiment should be held in a room with a constant temperature. A more sensitive voltmeter would also make the experiment more precise. ?? ?? ?? ?? 1 6 ...read more.

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