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How does the current of a cell affect the percentage change in mass of the copper strip on the negative electrode?

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Introduction

Rammy Abssi Chemistry - 11 December 16, 2009 Redox Planning Lab Research Question/Aim: How does the current of a cell affect the percentage change in mass of the copper strip on the negative electrode? The aim of this experiment is to record how the change in current of the cell changes the percentage change in mass of the copper strip. Basically, the percentage change in mass will be taken from the negative electrode because the negative electrode is where the reduction occurs and the mass will increase. The current will be increased by increasing the voltage of the cell and the certain current will be recorded for 6V, 8V, 10V, 12V, and 14V. Type of Variable Variable Range of Values/Method of Control Independent Variable Current of Cell 0.28, 0.57, 0.86, 1.17, and 1.43 amps Dependent Variable Average Percentage Change in Mass Controlled Time of Reaction 300 seconds in all trials Concentration of Solution 1 molar Volume of Solution 200cm3 Type of Solution Copper (II) Sulfate Material on Electrodes Solid Copper Strips Variables: Materials: * 250ml beaker * 200ml of 1 molar Copper (II) Sulfate * 30 copper strips * Power supply (up to 14V) * Stop watch * Balance * Crocodile clips * Red and black wires * Ammeter Picture: Method: There will be three trials for each of the five different currents. ...read more.

Middle

To process the data there are multiple steps. An example of how to process the data into Average Percentage Change in Mass is shown below: First, the average of the final mass must be calculated: (0.57 + 0.60 + 0.47) / 3 = 0.55 g Then, after the average final mass is calculated the following formula is used: = 7.8% Therefore, the average percentage change when the currant is 0.28 amps is 7.8%. Table 2: Processed Data: Average Percentage Change in Mass at Different Currants of the Cell Currant of Cell (amps) � 0.01 amps Average Percentage Change in Mass (%) 0.28 07.8 0.57 14.9 0.86 18.9 1.17 25.0 1.43 28.9 Qualitative Results: * The copper strip on the positive electrode became a little black and some black debris began to fall off of it when it was in the solution. * When I was holding the copper strips in the solution, and my hands were still, the current stayed constant; however, when I put the copper electrodes further in the solution the current increased a little. This shows that surface area could have an effect on the currant. * The color of the solution did not change throughout the whole experiment; therefore, the concentration stayed constant. Graph: The error bars on the graph above represent the range of values, of percentage change in mass, for each currant. ...read more.

Conclusion

This changes the surface area of the reactant and that would have a greater affect on the results. For example, if one of the trials had 0.50 grams of sodium carbonate-deca-hydrate and there was a big piece of that substance, than the surface area of those 0.50 grams would be less than the surface area of the trial that had all powder substance. With a larger surface area there would be fewer collisions which would make the rate of the reaction slower. Directly affecting the results, this limitation would need to be improved. A realistic improvement to this experiment would be to simply use a bowl and crush all the sodium carbonate-deca-hydrate to powder. Therefore, there would be no big pieces and the surface area would be relatively the same in each trial. Another limitation to this experiment would be the fact that the sodium carbonate-deca-hydrate was poured into the test tube right before the one hole stopper was placed on the test tube. Therefore, there was a small time frame where gas was lost. This would affect the pressure in the test tube. One simple way to improve this limitation would be to use a special test tube. with this special test tube there should be a small hole on the side where another tube comes out and that is where the sodium carbonate-deca-hydrate would be placed in. Therefore, there would be minimal or no gas escaping and the results would not be affected by a drop in pressure. ...read more.

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