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How does concentration affect the rate of electrolysis of Copper Sulphate solution?

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Introduction

How does concentration affect the rate of electrolysis of Copper Sulphate solution? Aim: In order to find out what factors affect the rate of electrolysis, we will change the concentration of the solution to find out which produces the highest current. Background information: Electrolysis is defined as: "The breakdown of a chemical substance by electricity." The following is the formula for what happens during electrolysis of Copper Sulphate Solution: 2CuSO4 (AQ) + 2H2O (L) 2Cu (S) + O2 (G) + 2H2SO4 (AQ) Reaction in the solution Copper + Oxygen + Sulphuric Acid Variables: The following is a list of variables that could effect the experiment: Table 1 Variable: Effect: Controlled: The concentration of the solution This is expected to effect the results, and will be the focus of the experiment. This will be the variable for the experiment The voltage flowing through the circuit With a higher voltage, the cathode would produce more copper Yes, the voltage will always be kept the same (9 volts) The temperature of the solution If the temperature is increased then the molecules will move faster and therefore more copper and oxygen will be produced. It will be kept at approximately 22 � C, (room temperature) but the temperature will be measure before and after the experiment The size of the beaker & The surface area of the electrodes that are in contact with the water. ...read more.

Middle

It must also be noted that Copper Sulphate Solution is poisonous, and the nitric acid is also very dangerous, therefore extra care will be taken around these two liquids. Diagram: Fig. 1 Results: The following tables are the results gathered from the experiment. Table 2 is the initial test, and tables 3 and 4 are the 'backup' tests that are taken in order to acquire an average in case of any errors in one particular recording. First experiment: Table 2 Concentration (ml) Current (MA) Temperature (�C) Color Before Experiment Mol/dm� water Initial End 0.5 0.5 0.61 24 25 Light Blue to Blue 0.6 0.4 0.83 23.5 24 Slightly Darker Blue 0.7 0.3 0.89 23 24.5 Still slightly darker, now medium blue 0.8 0.2 0.99 24 25 Darker, now almost dark blue 0.9 0.1 1.28 24.5 25.5 Darker still, verging on dark blue 1 0 1.24 23 24 Darkest yet, now dark blue. For the following experiments, (table 3 and 4) the color was not recorded, as it looked the same as previously stated in experiment one (table 2). Second experiment: Table 3 Concentration (ml) Current (MA) Temperature (�C) mol/dm� water Initial End 0.5 0.5 0.77 23 24 0.6 0.4 0.64 22.5 23.5 0.7 0.3 0.8 22.5 23.5 0.8 0.2 0.83 23 23.5 0.9 0.1 0.76 23 24 1 0 0.98 23 23.5 The yellow highlighted results shown in tables 3 (above) ...read more.

Conclusion

Also, for further investigation I could have weighed the electrodes directly after the experiment, to ensure that the only mass gained was through the extra copper. In addition the final weight of the electrodes could be measured at the end of each experiment, to attempt to determine the weight of copper deposited. Also, I could change the voltage on the power supply instead of keeping it at a constant 9 volts. This would give a more varied set of results that I could gather the average of. Finally, I to ensure better results I could try and use the exact same wires and the same electrodes along with keeping up with all the constants that are already in the experiment (such as the size of the beaker). Overall, the best-fit line (shown in Fig. 3) shows that this experiment was a success. The results indicate an upward trend between the concentration of the Copper Sulphate Solution and the Current recorded. Therefore showing that this experiment was a success. It is likely that even if this experiment was to be repeated the results would be similar and the best-fit line generated would be very similar, if not identical due to the fact that the anomaly shown is only just outside the margin of error. Through this experiment, it has been determined that an increase in the density of the concentration of Copper Sulphate Solution results in a higher rate of electrolysis, or an increase in the recorded current. Richard Coppock 1 ...read more.

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