Chemistry C6 4.0 / 5 based on 2 ratings ? ChemistryGCSEOCR Created by: Mollie DerhunCreated on: 29-01-13 19:40 ELECTROLYSIS & FUEL CELLS Electrolysis is the flow of charge by moving ions and the discharge of ions at electrodes An ionic solid cannot be electrolysed as the ions are in a fixed position and cannot move The amount of substance produced during electrolysis increases as current increases and as time increases The reaction between hydrogen and oxygen is 2H₂ + O₂ = 2H₂O Advantages of using hydrogen-oxygen fuel cells in a spacecraft: no moving parts, compact and lightweight and provide water for the astronauts Fuel cells are being developed by the car industry because they need to find fuels that are renewable and less polluting 1 of 4 REDOX & ALCOHOLS Redox reactions involve both reduction and oxidation Iron can be protected from rusting by using a sacrificial metal The optimum temperature for fermentation is 25-50⁰C If the temperature is too low, the enzymes in the yeast are inactive If the temperature is too high, the enzymes in the yeast are denatured The molecular formula of ethanol is C₂H₅OH The molecular formula of butanol is C₄H₉ Alcohol can also be made from ethene, ethene + water = ethanol Fermentation of glucose = carbon dioxide + ethanol 2 of 4 THE OZONE LAYER CFC's have been banned in the UK as they lead to the depletion of the ozone layer More ultraviolet light can reach the surface of the Earth if the ozone layer is depleted Ultraviolet light on CFC's makes highly reactive chlorine atoms. These chlorine atoms in the stratosphere cause the depletion of the ozone layer CFC's can be replaced with alkanes or HFC's as these will not damage the ozone layer 3 of 4 WATER, OILS AND DETERGENTS Temporary hardness is caused by calcium hydrogencarbonate, which is removed by boiling Hardness in water can be removed by passing the water through an ion-exchange column Immiscible liquids, such as vegetable oild and water, form an emulsion when shaken with an emulisifier Detergent molecules have a hydrophillic head and a hydrophobic tail There are weak intermolecular forces between molecules of oil. Solvent molecules make intermolecular forces with molecules of grease so that solvent molecules can surround molecules of grease 4 of 4
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