C2.7 Electrolysis

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GCSE Chemistry (C2) Mind Map on C2.7 Electrolysis, created by killthemoment on 07/26/2014.

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C2.7 Electrolysis
1 C2.7.1 Electrolysis
1.1 Ionic compounds have many uses and can provide other substances. Electrolysis is used to produce alkalis and elements such as aluminium, chlorine and hydrogen.
1.1.1 Electrolysis is the process by which ionic substances are broken down into simpler substances using electricity. During electrolysis, metals and gases may form at the electrodes. For electrolysis to work, the ions must be free to move; either in solution or molten. Passing an electric current through ionic substances that are molten or in solution breaks them down into elements. This process is called electrolysis and the substance that is broken down is called the electrolyte. During electrolysis, positively charged ions move to the negative electrode, and negatively charged ions move to the positive electrode. Electrolysis is used to electroplate objects: the negative electrode should be the object that is to be electroplated; the positive electrode should be the metal that you want to coat the object with; the electrolyte should be a solution of the coating metal, such as its metal nitrate or sulfate. At the negative electrode, positively charged ions gain electrons (reduction) and at the positive electrode, negatively charged ions lose electrons (oxidation). If there is a mixture of ions, the products formed depend on the reactivity of the elements involved. Reactions at electrodes can be represented by half equations, for example: 2CL− → CL2 + 2e−. Aluminium is manufactured by the electrolysis of a molten mixture of aluminium oxide and cryolite. Aluminium forms at the negative electrode and oxygen at the positive electrode. The positive electrode is made of carbon, which reacts with the oxygen to produce carbon dioxide. The electrolysis of sodium chloride solution produces hydrogen and chlorine. Sodium hydroxide solution is also produced. These are important reagents for the chemical industry, eg sodium hydroxide for the production of soap and chlorine for the production of bleach and plastics.
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