Title: Does changing the concentration of the electrolyte have an effect on the mass of the plating around the cathode in an electrolytical cell?
Aim: To investigate how changing the concentration of the electrolyte influences mass of plating around the cathode in an electrolytic cell.
Hypothesis: If we Increase the concentration of the copper electrolyte, in an electrolytic cell, there will be a greater mass of copper plating
around the cathode, because increasing the concentration of the electrolyte will increase the frequency of collisions between the electrode and
the electrolyte, resulting in a greater amount of plating in mass around the cathode.
Background concepts:
Collision theory: Collision theory states that when particles gain energy, they move faster and collide with other particles more frequently.
Methodology:
1.
2.
3.
4.
5.
Weigh the copper strip before setting up the cell
Assemble the electrolytic cell as shown.
Pour 60ml of 0.1M copper sulphate solution into the 100ml beaker, and set the battery pack to 4V
Run the cell for 5 minutes and while recording the current, and turn it off after 5 minutes have passed
Remove the copper strip carefully and fully submerge the plated area into the acetone. Then into water and let it air dry until there is no
visible moisture on the strip.
6. Weigh the copper strip and subtract this mass to the mass recorded before the experiment, to determine the mass of the plating.
Record the results on a table.
7. Repeat steps 1-6 two more times with 0.1M of copper sulphate, and 3 times using different copper strips for 0.5M and 1M of copper
Sulphate, and only once with water as a control variable.
Discussion:
In the experiment our experimental results were 0.022g of plating in 1M, 0.017g in 0.5M and 0.005 g plating in 0.1M of copper sulphate. The
expected results were 0.025g for 1M, 0.018 for 0.5M and 0.007g for 0.1M. Since our experimental results are close to the expected results, it
shows that our results were accurate.
An explanation to the pattern that can be seen to the left is that
Random error: Surface Area of Cathode. Since we used Different cathodes for each test, the surface area could have been different. This could
have slightly reduced the accuracy of our results. In the future we can control this by measuring the same surface area of the cathode.
Systematic error: Amount of copper plating dropped from the cathode when removing it from the cell, which could affect the precision of the
results. In the future we can control this by slightly reducing the current which could reduce the amount of plating around the cathode, thus
reducing the amount falling off.
We conducted three tests for each concentration to get the average result, improving our precision. Additionally, we used water as a control to
check for any external sources that could affect the mass. However, due to operator error it showed that the mass decreased and was not used
in the results.
Conclusion:
Our experiment was successful, as we were able to answer the aim of our investigation, that increasing the concentration of the electrolyte in
an electrolytic cell, increased the mass of plating. Additionally, our hypothesis was supported, as increasing the concentration did increase the
mass of plating on the cathode, for instance 1M produced 0.022g, 0.5M produced 0.017g and 0.1M produced 0.005 g of plating. Lastly, the
main limitation of our experiment was that we could only control the voltage and not the current. So, we cannot fully confidently say that
increasing the concentration of the electrolyte increases the mass of plating, as each concentration had different currents.