Overall, you should end up with 3 initial masses and 3 final masses for each of the five different voltages/currants. These results will later be calculated to find the average percentage change in mass.
Results:
Table 1: Raw Data: How the Curran of the Cell Affected the Change in Mass of the Copper Strip on the Negative Electrode
Processing Raw Data:
The table above shows the raw data collected from this experiment. 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
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.
Calculations:
Percentage Uncertainty:
Currant:
(0.01/0.28) x 100% = 3.6%
(0.01/0.57) x 100% = 1.8%
(0.01/0.86) x 100% = 1.2%
(0.01/1.17) x 100% = 0.9%
(0.01/1.43) x 100% = 0.7%
Average Initial Mass:
(0.01/0.51) x 100% = 2.0%
(0.01/0.47) x 100% = 2.1%
(0.01/0.53) x 100% = 1.9%
(0.01/0.48) x 100% = 2.1%
(0.01/0.52) x 100% = 1.9%
Average Final Mass:
(0.01/0.55) x 100% = 1.8%
(0.01/0.54) x 100% = 1.9%
(0.01/0.63) x 100% = 1.6%
(0.01/0.60) x 100% = 1.7%
(0.01/0.67) x 100% = 1.5%
Total Percentage Uncertainty: 26.7%
Percentage Error:
To find the percentage error, the theoretical values for all the currants need to be found: this is shown bellow using Faraday's constant.
Faraday's constant = electrical charge of 1 mol of electrons = 96500 Cmol-1
Conclusion:
Overall, the hypothesis held correct. Clearly shown from the results, the rate of the reaction was much faster when the molar concentration of the reaction was greater. The rate of the reaction was measured using a pressure sensor, and as the rate of the pressure would indicate the rate of the reaction. For the one molar concentration of hydrochloric acid the rate of the reaction was about twice as fast as the half molar concentration. This can clearly be explained through kinetics. The more concentrated one of the reactants is the more particles there will be. Therefore, when there are more particles more collisions will occur and with more collisions the chances of the collisions being greater than the activation energy will also increase. Overall this increases the rate of the reaction.
Evaluation:
Overall, this experiment went very well; however, there were numerous limitations which affected the results. One very clear and important limitation is the fact that not all the sodium carbonate-deca-hydrate was powder. During the experiment, 0.50 grams of sodium carbonate-deca-hydrate was collected for each trial of the experiment. However, not all the sodium carbonate-deca-hydrate was powder, as there were some larger pieces. 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.
