![]() At the anode (positive electrode), negatively charged ions lose electrons and so the reactions are oxidations. During electrolysis, at the cathode (negative electrode), positively charged ions gain electrons and so the reactions are reductions.4.4.3.5 Representation of reactions at electrodes as half equations (HT only).For example, copper can be obtained from solutions of copper compounds by displacement using scrap iron or by electrolysis. The metal compounds can be processed to obtain the metal.4.10.1.4 Alternative methods of extracting metals (HT only).4.10.1 Using the earth's resources and obtaining potable water.Electrolysis of (i) copper sulfate solution with copper electrodes and (ii) acidified water with inert electrodes.(n) electrolysis of aqueous solutions such as copper(II) chloride (including electrode equations).Unit 2: CHEMICAL BONDING, APPLICATION OF CHEMICAL REACTIONS and ORGANIC CHEMISTRY.Conduction in ionic compounds can be explained by the movement of ions towards oppositely charged electrodes.Atomic structure and bonding related to properties of materials.This is to confirm that the mass gained at the cathode is equal to the mass loss at the anode. The electrolysis can be done using two weighed copper strips.the cathode is made of pure copper or a support metal such as stainless steel.the anode consists of an unrefined sample of the metal.This leads to a discussion as to why, during electrolytic refining: Students can then see the copper disappearing from the surface of the copper-coated anode: After doing the electrolysis as described above, the electrodes can be interchanged.Extension experiments for copper refining ![]() It is wise not to complicate electrolytic deposition with chemical displacement – valued articles can be effectively ruined. This happens for instance in items made of metals above copper in the reactivity series. In many cases, an alternative redox reaction often takes place before any current is actually passed. It can be instructive to allow students to copperplate metal objects supplied by the school and previously tested for their suitability. The results of this experiment can lead to a discussion about electroplating and the electrolytic refining of copper. The reaction is the reverse of the cathode reaction. If copper is used for the electrodes, the copper anode dissolves. With carbon (graphite) electrodes, the oxygen usually reacts with the anode to form CO 2. You should explain that, if the current used is much lower, then the solid coating is shiny, impermeable and very difficult to rub off this process forms the basis of electroplating.īubbles of gas (oxygen) are formed at the anode.Ĭathode reaction: Cu 2+(aq) + 2e - → Cu(s)Īnode reaction: 2H 2O(l) → O 2(g) + 4H +(aq) + 4e. Students should see a deposit of copper forming on the cathode. The cathodes can be cleaned using emery paper.Įquipment required for the electrolysis of copper(II) sulfate solution. They should watch for any activity on each of the electrodes, and write down their observations. Ask the students to set up the cell as shown.Copper(II) sulfate solution is HARMFUL if concentration is equal to or greater than 1 M. If the concentrations are increased, the solutions must be labelled with the correct hazard warnings. At the suggested concentrations, the copper(II) sulfate solution is LOW HAZARD. Copper(II) sulfate solution, CuSO 4(aq) – see CLEAPSS Hazcard HC027c and CLEAPSS Recipe Book RB031.Students must wash their hands at the end of all practical work. Read our standard health and safety guidance.Copper strips x2 (optional these can be used in place of the graphite rods as an extension to the basic experiment).Aqueous copper(II) sulfate, about 0.5 M, 200 cm 3.A bulb can be included in the circuit to indicate that there is a flow of current.They can also be fixed using Blutac onto a small strip of wood resting on the top of the beaker. Using a retort stand and clamp is probably the most convenient. There are several ways of securing the graphite electrodes.Light bulb, small, 6 volt, 5 watt (optional note 2).Retort stand and clamp to hold electrodes (note 1).Graphite electrodes, about 5 mm diameter, x2.This class experiment can be done by students working either in pairs or threes. With supporting resources, including illustrated technician notes, integrated instructions, pause-and-think questions, worksheets and more. Use our Electrolysis of aqueous solutions video to support you to deliver this practical lesson. ![]() RSC Yusuf Hamied Inspirational Science Programme. ![]()
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