¡Descarga electroplating lab report y más Guías, Proyectos, Investigaciones en PDF de Cultura Científica solo en Docsity!
Factors affecting the rate of the electroplating
Beatriz Sánchez Álvarez
Criteria B & C
M
Introduction:
What is electroplating?
Electroplating is the application of electrolytic cells in which a thin layer of metal is deposited onto an electrically conductive surface. A cell consists of two electrodes(one is the cathode and the other the anode) in this case they were a copper piece and a graphite. They are usually made out of metal, and held apart from one another. The electrodes are immersed in an electrolyte (a solution), in our case it was copper sulphate^1. When an electric current is turned on, positive ions in the electrolyte move to the negatively charged electrode, called the cathode. Positive ions are atoms with one electron too few. When they reach the cathode, they combine with electrons and lose their positive charge. At the same time, negatively charged ions move to the positive electrode, called the anode. Negatively charged ions are atoms with one electron too many. When they reach the positive anode, they transfer their electrons to it and lose their negative charge. Electroplating is usually used to improve the appearance of a base material, however, the technique is used for multiple other purposes. This includes the building of thickness, the protection of surfaces and some more...This uses of the technique have of course some benefits. These benefits include a protective barrier in the base material, an enhanced appearance, improved hardness, electrical conductivity: Silver and copper plating help improve electrical conductivity in parts, offering a cost-effective, efficient solution for improving conductivity in electronics and electrical components and last one but not least heat resistance^2. (^1) "Electroplating - Chemistry LibreTexts." 10 Dec. 2020, https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Modules_(Analytical_Chemi stry)/Electrochemistry/Electrolytic_Cells/Electroplating. Accessed 20 Jan. 2021. (^2) "The Uses for Electroplating - Sciencing." https://sciencing.com/uses-electroplating-8100658.html. Accessed 20 Jan. 2021.
Background knowledge: Electroplating is an electrolytic process. The metal foil providing the coating metal acts as an anode. The electrolyte is usually an ionic solution coated with metal. The object to be coated acts as a cathode. When a voltage charge is introduced between the anode and the cathode, it attracts the metal in the electrolyte. The ions swim towards the cathode, where they are coated after reduction. At the same time, the anode metal dissolves again, providing more metal ions in the electrolyte. Electrolysis is the process by which an electric current is passed through a substance to effect a chemical change. The chemical change is one in which the substance loses or gains an electron (oxidation or reduction). The process is carried out in an electrolytic cell, a device consisting of separate positive and negative electrodes immersed in a solution containing positively and negatively charged ions^3. To return to what was mentioned earlier, an oxidation-reduction (redox) reaction is a type of chemical reaction that involves a transfer of electrons between two species. An oxidation-reduction reaction is any chemical reaction in which the oxidation number of a molecule, atom or ion changes by gaining or losing an electron^4. So more generally, Electroplating is the coating of a metal object with another metal, using an electrical current passed through a chemical solution. This system is made up of: a cathode – the material to be plated , an anode – the plating metal or inert conductor, an electrolytic solution – a salt solution used to immerse the anode and cathode containing metal ions to be coated and an electrical current – provided by an electrical source such as a battery or other power unit. (^3) "Electrolysis - Chemistry LibreTexts." 15 Aug. 2020, https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Modules_(A nalytical_Chemistry)/Electrochemistry/Electrolytic_Cells/Electrolysis. Accessed 30 Jan.
(^4) "Oxidation-Reduction Reactions - Chemistry LibreTexts." 15 Aug. 2020, https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Modules_(Analytical_Chemistr y)/Electrochemistry/Redox_Chemistry/Oxidation-Reduction_Reactions. Accessed 30 Jan. 2021.
Independent variable:
● Time(s): 30, 60, 90, 120, 150
Dependent variable:
● Mass of copper(g) Equipment list: ● x1Power pack ● X1 Red/black wires ● X2 Crocodile clippers results. Voltage of the power pack: 6 volts It’s^ necessary^ to^ ensure^ hat^ the^ voltage is always at the same number otherwise there could be a big change in the results causing the mass of the graphite stick to increase or decrease. Mass of copper sulphate solution: 150ml The mass of the copper sulphate must remain the same throughout the experiment, otherwise the results will be different and unreliable. Distance between the electrodes: 15mm The^ distance between the graphite and the copper is very important because if there is a difference in separation in each experiment, the copper ions take longer to flow and that would make the copper ions take more or less time to reach the graphite. That would mean that it could reduce or increase the mass of the cathode. Concentration of sulphate solution: 1mole Make sure that the copper sulphate solution is always the same as the difference in the solution can cause the ions to move differently, which can lead to anomalies in the weight of the graphite stick. Accuracy of mass measurements: 3 d.p This last one is for when you are making the tables, it is important that you always set your numbers to 3 d.p. so that the results can be better and more reliable.
● X1 Cardboard ● X1 Copper metal ● X1 Graphite electrode ● X1 500ml Beaker ● 250 ml CuSo4(aq) 1.0 molar ● X1 Mass balance ● X2 Tissue paper ● X1 chronometer ● X1 scissors (photo taken by Parsa) Method:
- Start by collecting all the material mentioned above, make sure you cut a piece of cardboard and a piece of copper.
- pour 150ml of copper sulphate into the beaker.
- take a piece of cardboard and make two holes in it
- Connect the power supply, but leave it off
- put the red wire in the indicated place as well as the black one
- take the crocodile clips and apply them to the end of the wires
Graph: Analysis: The graph above visually explains how the longer the cathode and anode are immersed in the 1 molar copper sulphate solution and connected to a power supply with a voltage of 6 the difference in mass increases. It can be seen that the first difference is the largest as it goes from 0.031 to 0.036 making a difference of 0.005 unlike the other points which all have a smaller change between them, the last two points do not even have a change in Potential Difference Time(s) mass increase (g) test 1 test 2 test 3 30 17.000 12.000 6. 60 0.020 0.014 0. 90 0.013 0.019 0. 120 0.022 0.016 0. 150 0.020 0.015 0.
mass, which indicates that the ions moved equally being immersed for 120 seconds and 150 seconds. However, it can be seen that the correlation line rises slightly making an upward slope. Conclusion: The graph and tables show how longer the cathode and anode are immersed in the copper sulphate solution, means that more e- con flow so the rate of a redox reaction will be quicker and the mass of the cathode will increase as time passes. I can also conclude that there is a point (125s) where no matter the time the ions move they are the same. With the observation of the graph and the tables I can deduce that there is some anomaly. The third point on the graph and therefore in the middle of the second test the results obtained after the experiment are a bit anomalous. This is due to the fact that the experiment was done in two classes, on different days. When the cathode was left to stand, all the copper sulphate solution it had absorbed was consumed, so when it was weighed after standing it weighed less and this caused anomalies to occur. That is why it can be seen that it simply went from 0.036 to 0.037. However, there was a minor increase in the last two points. Still you can conclude that my hypothesis was correct and that the longer the anode and cathode are immersed in the copper sulphate solution the thicker the coating becomes and the heavier it becomes. You can confirm my justification, I had said that when an electric current is turned on, positive ions in the electrolyte move to the negatively charged electrode, called the cathode. Positive ions are atoms with one electron too few. When they reach the cathode, they combine with electrons and lose their positive charge. At the same time, negatively charged ions move to the positive electrode, called the anode. Evaluation: Limitations How could I overcome these problems if I were to repeat this experiment again? One of the limitations was to have done the experiment in two different classes and on different days. This problem caused anomalies in my results, the only way to deal with this problem is to have started the experiment on a day when we had two hours of science class, so that at least some of the anomalies would be reduced. A second limitation was to use the same When we did the experiment, other groups
