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Electrolysis of aquatic salt solution

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SC1 Physics Mr. Poore Group 1 Kelly Wainwright 10DB Electrolysis of aquatic salt solution I am going to investigate what elements are made at the electrodes and if there is a pattern. The input variable is: * The solution I use The out come variables are: * The element at cathode * The element at anode The controlled variables are: * The voltage of the power pack * The concentration of the solution Electrolysis is the process by which an electric current is passed through a substance which will result in a chemical change. The chemical change is one in which the substance loses or gains electrons (oxidation or reduction). The process is carried out in an electrolytic cell , an apparatus consisting of positive and negative electrodes held apart and dipped into a solution containing a compound. The substance to be transformed may form the electrode, may make up the solution, or may be dissolved in the solution. The electric current enters through the negatively charged electrode (the cathode). In my investigation I think that the element at the cathode will be a metal. This because metals have a plus charge and are attracted to the negative cathode to gain electrons. 3Al+ + 3e- Al3 Cu2+ + 2e- Cu2 At the anode I expect to get a non-metal. This because non-metals have minus charges and are attracted to the positive anode to give electrons. ...read more.


I read the safety cards for the chemicals we had to use. I wore goggles and protective gloves when handling the compounds I found out the tests for the gases like: * Chlorine - a green gas that bleaches litmus paper * Hydrogen - a colourless gas that pops if heated up. * Oxygen - a colourless gas that will relight a glowing splint. * Bromine - a brown gas. * Iodine - A purple gas. My Results: After doing the electrolysis of the solutions I notice at the cathode the element produce was either Hydrogen or a metal. The metals were low down in the reactivity series. At the anode it was a gas. Either Oxygen or a gas from group 7 in the Periodic Table e.g. Bromine (Br). My results support my prediction. This is because I thought that negatively charged ions (either the Hydroxide atoms or the non-metal atoms) would go to the anode, which they did. And that positively charged ions (either the Hydrogen atoms or the metal atoms) would go to the cathode, which they did. However I couldn't predict which atoms of the two would escape. Starting with the cathode, either the Hydrogen ion (H+) or the metal ion (e.g. cooper Cu2+) would escape and the other would be left in the solution. The question is, which one. After looking carefully at my results I saw that the only metals that would escape the solution were the ones that were below Hydrogen. ...read more.


Another factor which may have affected the overall outcome of the investigation, may have been the fact that the practical work of the investigation was carried over from lesson to lesson, meaning that variables such as the concentration or the amount of the aquatic salt solution could have changed between lessons. To overcome this problem, the same electrodes and equipment should have been used throughout. To further this investigation I should investigate more of the variables in this experiment, which may or may not affect the different elments deposited onto the cathode and anode, such as changing the Current or Temperature variable. To carry on with this experiment I decided to see how the rate of electrolysis was affected by amount of electricity flowing around the electrodes. For this experiment I did the electrolysis of Sulphuric acid (HSO4). I think if you increase the flow of electricity the volume of Hydrogen will increase. This is because the flow of electrons go to the cathode, the hydrogen ions collects the electrons and become hydrogen. The faster the electrons flow, the greater volume of Hydrogen will be made. I tested the electrolysis of HSO4 every five minutes at 0.6 Amps, 0.8 Amps and 1.4 Amps. These are the results I got: My results support my prediction; the faster the electrons flow the greater the increase of Hydrogen is. 2H+ + 2e- H2 Overall my experiment went well. Even though the gases and metals were hard to collect, the results hold up to my prediction. ...read more.

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