Electrolysis

Electrolysis
Electrolysis In chemistry, the production of chemical changes by passing an electric current through a solution or molten salt (the electrolyte), resulting in the migration of ions to the electrodes: positive ions (cations) to the negative electrode (cathode) and negative ions (anions) to the positive electrode (anode). During electrolysis, the ions react with the electrode, either receiving or giving up electrons. The resultant atoms may be liberated as a gas, or deposited as a solid on the electrode, in amounts that are proportional to the amount of current passed, as discovered by English chemist Michael Faraday. For instance, when acidified water is electrolysed, hydrogen ions (H+) at the cathode receive electrons to form hydrogen gas; hydroxide ions (OH-) at the anode give up electrons to form oxygen gas and water. One application of electrolysis is electroplating, in which a solution of a salt, such as silver nitrate (AgNO3), is used and the object to be plated acts as the negative electrode, thus attracting silver ions (Ag+)
Electrolysis is used in many industrial processes, such as coating metals for vehicles and ships, and refining bauxite into aluminium; it also forms the basis of a number of electrochemical analytical techniques, such as polarography. Faraday?s laws ====== Three laws of electromagnetic induction, and two laws of electrolysis, all proposed originally by English scientist Michael Faraday: Induction (1) a changing magnetic field induces an electromagnetic force In a conductor; (2) the electromagnetic force is proportional to the rate of change of the field; (3) the direction of the induced electromagnetic force depends on the orientation of the field. Electrolysis (1) the amount of chemical change during electrolysis is proportional to the charge passing through the liquid; (2) the amount of chemical change produced in a substance by a given amount of electricity is proportional to the electrochemical equivalent of that substance. Faraday?s constant ====== Constant (symbol F) representing the electric charge carried on one mole of electrons. It is found by multiplying Avocado?s constant by the charge carried on a single electron, and is equal to 9.648 × 104 coulombs per mole. One faraday is this constant used as a unit. The constant is used to calculate the Electric charge needed to discharge a particular quantity of ions during Electrolysis. Faraday, Michael (1791-1867) English chemist and physicist. In 1821, he began experimenting with electromagnetism, and discovered the induction of electric currents and made the first dynamo, the first electric motor, and the first transformer. Faraday isolated benzene from gas oils and produced the basic laws of electrolysis in 1834.He also pointed out that the energy of a magnet is in the field around it and not in the magnet itself, extending this basic conception of field theory to electrical and gravitational systems. Chemistry and the discovery of benzene Faraday was mainly interested in chemistry during his early years at the Royal Institution. He investigated the effects of including precious metals in steel in 1818, producing high quality alloys that later stimulated the production of special high-grade steels. In 1823, Faraday produced liquid chlorine by heating crystals of chlorine hydrate in an inverted U- tube, one limb of which was heated and the other placed in a freezing mixture. After the production of liquid carbon dioxide in 1835, he used this coolant to liquefy other gases. In the same year, Faraday isolated benzene from gas oils and demonstrated the use of platinum as a catalyst. He also demonstrated the importance in chemical reactions of surfaces and Inhibitors, foreshadowing a huge area of the modern chemical industry. Laws of electrolysis ==== Faraday?s laws of electrolysis established the link between electricity and chemical affinity, one of the most fundamental concepts in science. Electrolysis is the production of chemical changes by passing an electric current through a solution. It Was Faraday who coined the terms anode, cathode, cation, anion, electrode, and electrolyte. He postulated that, during the electrolysis of an aqueous electrolyte, positively- charged cations move towards the negatively-charged cathode and negatively-charged anions migrate to the positively charged anode. Faraday demonstrated that the ions are discharged at each electrode according to the following rules: (a) The quantity of a substance produced is proportional to the amount of electricity passed; (b) The relative quantities of different substances produced by the same amount of electricity are proportional to their equivalent weights (that is, the relative atomic mass divided by the oxidation state or valency). Electromagnetism and the electric motor in 1821, only one year after Hans Oersted had discovered with a compass needle that a current of electricity flowing through a wire produces a magnetic field, Faraday was asked to investigate the phenomenon of electromagnetism by the editor of the Philosophical Magazine. Faraday conceived that circular lines of magnetic force reproduced around the wire to explain the orientation of Oersted?s compass needle. Faraday?s conviction that an electric current gives rise to lines of magnetic force arose from his idea that electricity was a form of vibration and not a moving fluid. He believed that electricity was a state of varying strain in the molecules of the wire conductor, and that this gave rise to a similar strain in the medium surrounding the conductor. It was reasonable to consider therefore that the transmitted strain might set up a similar strain in the molecules of another nearby conductor. Faraday set about devising an apparatus that would demonstrate the conversion of electrical energy into motive force. His device consisted of two vessels of mercury connected to a battery. Above the vessels and connected to each other were Suspended a magnet and a wire, which were free to move and dipped just below the surface of the mercury. In the mercury were fixed a wire and a magnet respectively. When the current was switched on, it flowed through both the fixed and free wires, generating a magnetic field in them. This caused the free magnet to revolve around the fixed wire, and the free wire to revolve around the fixed magnet. The experiment demonstrated the basic principles governing the electric motor. Although the practical motors that subsequently developed had a very different form to Faraday?s apparatus, he is usually credited with the invention of the electric motor. Electromagnetic induction and the transformer Faraday hunted for the effect of Electromagnetic induction from 1824 onwards, expecting to find that a magnetic field would induce a steady electric current in a conductor. Faraday eventually succeeded in producing induction in 1831. He wound two coils around an iron bar and connected one to a battery and the other to a galvanometer (an instrument for detecting small electric currents by their magnetic effect). Nothing happened when the current flowed through the first coil, but Faraday noticed that the galvanometer responded whenever the current was switched on or off. Faraday found an immediate explanation with his lines of force. If the lines of force were cut - that is, if the magnetic field changed ? then an electric current would be induced in a conductor placed within the magnetic field. The iron bar helped to concentrate the magnetic field, as Faraday later came to understand, and a current was induced in the second coil by the magnetic field momentarily set up as current entered or left the first coil. With this device, Faraday had discovered the transformer, a modern transformer being no different in essence even though the alternating current required had not then been discovered. Faraday is thus also credited with the simultaneous discovery of electromagnetic induction, although Joseph Henry had made the same discovery in the same way in 1830. However, busy teaching, Henry had not been able to publish his findings before Faraday did, although both men are now credited with the independent discovery of induction. Arago?s wheel and the electric generator in 1824, Francois Arago found that a rotating non-magnetic disc, specifically of copper, caused the deflection of a magnetic needle placed above it. This was in fact a demonstration of electromagnetic induction, but nobody at that time could explain `Arago?s wheel´. Faraday realized that the motion of the copper wheel relative to the magnet in Arago?s experiment caused an electric current to flow in the disc, which in turn set up a magnetic field and deflected the magnet. He set about constructing a similar device in which the current produced could be led off, and built the first electric generator in 1831. It consisted of a copper disc that was rotated between the poles of a magnet; Faraday touched wires to the edge and centre of the disc and connected them to a galvanometer, which registered a steady current. Electrostatic charge In 1832 Faraday showed that an electrostatic charge gives rise to the same effects as current electricity. He demonstrated in 1837 that electrostatic force consists of a field of curved lines of force, and that different substances have specific inductive capacities ? that is, they take up different amounts of electric charge when subjected to an electric field. In 1838, he proposed a theory of electricity elaborating his idea of varying strain in molecules. In a good conductor, a rapid build-up and breakdown of strain took place, transferring energy quickly from one molecule to the next. This also accounted for the decomposition of compounds in electrolysis. At the same time, Faraday wrongly rejected the notion that electricity involved the movement of any kind of electrical fluid (the motion of electrons is involved). However, in that this motion causes a rapid transfer of electrical energy through a conductor, Faraday?s ideas were valid. Polarization of light ===== Finally, Faraday considered the nature of light and in 1846 arrived at a form of the electromagnetic theory of light that was later developed by Scottish physicist James Clerk Maxwell. In 1845, Lord Kelvin suggested that Faraday investigate the action of electricity on polarized light. Faraday had in fact already carried out such experiments with no success, but this could have been because electrical forces were not strong. Faraday now used an electromagnet to give a strong magnetic field instead and found that it causes the plane of polarization to rotate, the angle of rotation being proportional to the strength of the magnetic field. Paramagnetic and Diamagnetism ========= Several further discoveries resulted from this experiment. Faraday realized that the glass block used to transmit the beam of light must also transmit the magnetic field, and he noticed that the glass tended to set itself at right-angles to the poles of the magnet rather than lining up with it as an iron bar would. He showed that the differing responses of substances to a magnetic field depended on the distribution of the lines of force through them. He called materials that are attracted to a magnetic field paramagnetic, and those that are repulsed diamagnetic. Faraday then went on to point out that the energy of a magnet is in the field around it and not in the magnet itself, and he extended this basic conception of field theory to electrical and gravitational systems. Faraday was born in Newington, Surrey, and was apprenticed to a bookbinder; he was largely self- educated. In 1812, he began researches into electricity, and made his first electrical cell. He became a laboratory assistant to Humphry Davy at the Royal Institution in 1813, and in 1833 succeeded him as professor of chemistry. Faraday delivered highly popular lectures at the Royal Institution 1825-62. He refused to take part in the preparation of poison gas for use in the Crimean War. Aim: I shall conduct an experiment, which will see how much copper is deposited during the electrolysis of copper sulphate. Copper Sulphate is the electrolyte of this experiment. Electrodes are materials connected to the negative terminal of the negative terminal of the battery and is called Cathode the electrode connected to the positive terminal of the battery is Anode. Many factors will effect this experiment time, as there is a limited time to conduct this experiment due to class period. ? Time ? Current ? Concentration Of Solution ? Temperature ? Distance Between Electrodes ? Quantity Of Solution ? Size Of Electrodes Predictions: I think that if you put more current you should get more copper deposited as the current passes quicker thought the circuit. You can calculate how much copper will be deposited at the cathode by using the following equation: Q=I*T Where Q=Amount of charge (electrons) in coulombs I=Current in amps T=Time in seconds I think during electrolysis, copper ions are will be attracted towards the positive anode. Copper atoms which make up the anode each will give up two electrons to form CU2+ ions. The overall result I think will be that the anode loses weight as the cathode gains weight. Below are some of my predicted results which I complied from my preliminary experiments. Predicted Results Voltage Current Time Cathode before Cathode after Anode before Anode after Cathode difference Anode difference 4.5 1.00 10min 1.5 1.16 1.8 1.6 0.11+ -0.2 4.5 1.23 20min 1.6 2.0 1.7 1.4 0.4+ -0.3 4.5 1.30 30min 1.9 2.1 1.4 1.1 0.2+ -0.3 4.5 1.70 35min 2.1 2.5 1.4 1.2 0.4+ -0.2 6 1.00 10min 1.9 2.0 1.7 1.6 0.1+ -0.1 6 1.11 20min 1.9 2.1 1.8 1.4 0.2+ -0.4 6 1.19 30min 1.9 2.3 1.9 1.4 0.5+ -0.5 6 0.83 35min 1.5 1.6 2.4 2.2 0.1+ -0.2 [image] [image] Equipment:
Two Copper Electrodes[Anode(+)Cathode(-)]
Beaker
Voltmeter
Ammeter
Copper Sulphate Solution
Battery Power Pack
Splints
Crocodile Clips
Circuit Wires
Method: I first with my friend?s we gathered all necessary equipment for this experiment we got Two Copper Electrodes, A Beaker ,Voltmeter, Ammeter, Copper Sulphate Solution, Battery Power Pack and some Splints. I set the equipment as shown in the diagram below. I got a beaker and poured 500ml of Copper Sulphate Solution. The Copper Electrodes were then placed into the solution and then were held against the beaker with splints. I connected up the wires to the battery pack then to the ammeter and to the electrodes at the wire that?s going towards the electrodes we added Crocodile Clips and then clipped it on to the Copper Electrodes. We then used two different voltages 4.5 and 6 we used the two different voltages with different times. They were 10min, 20min, 30min, 35 min we used these times on both the different voltages. We stopped them at these times to record the difference in weight at the beginning of the experiment. At this time we turned of the current and weighted the Electrodes. We looked at the solution, current, the weight of the copper electrodes; we looked at all of these at the end of each experiment. During the experiment we noticed that the current fluctuated and that there was the impure Copper left at the bottom of the beaker as Sludge

Electrolysis 7.5 of 10 on the basis of 2072 Review.