Changing the Temperature Suppose the forward reaction was exothermic A + 2B C + D = -100 kJ mol-1 ∆H This would mean that the back reaction would be endothermic by the same amount (-100 kJ mol-1). Suppose the temperature was decreased, the reaction would respond by increasing the temperature back up again. This can only be done by producing more C and D because the forward reaction is exothermic. Increasing the temperature will of course, have the opposite effect. Adding a Catalyst Adding a catalyst speeds up the forward and back reactions by the same proportion. This means that there is no change in the position of the equilibrium. Methods of Extraction The extraction of metals depend alot on its position in the reactivity series. are also factors to take into account. For metals up to zinc, the cheapest method is usually heating the ore with carbon or carbon monoxide to reduce it. For metals more reactive than zinc, electrolysis is usually used. The Extraction of Aluminium Aluminium is extracted from an ore called bauxite, which is impure aluminium oxide. Aluminium ions are attracted to the cathode and are reduced to aluminium: Al3+ + 3e- Al Oxide ions are attracted to the anode and lose electrons to form oxygen gas: 2O2- O2 + 4e- There are a few things to keep in mind: Melting aluminium requires extremely high temperatures. Instead, it is dissolved in an aluminium compound called cryolite. Because of high temperatures, the carbon anodes will burn with oxygen to form carbon dioxide. This means the anodes have to be replaced regularly. The cost of electricity is also a major factor the cell has currents up to 100 000A so it is expensive. – Uses of aluminium include: Use Property of Aluminium That This Useful
Changing the Temperature Suppose the forward reaction was exothermic A + 2B C + D ∆H = -100 kJ mol-1 This would mean that the back reaction would be endothermic by the same amount (-100 kJ mol-1). Suppose the temperature was decreased, the reaction would respond by increasing the temperature back up again. This can only be done by producing more C and D because the forward reaction is exothermic. Increasing the temperature will of course, have the opposite effect. Adding a Catalyst Adding a catalyst speeds up the forward and back reactions by the same proportion. This means that there is no change in the position of the equilibrium. Methods of Extraction The extraction of metals depend alot on its position in the reactivity series. are also factors to take into account. For metals up to zinc, the cheapest method is usually heating the ore with carbon or carbon monoxide to reduce it. For metals more reactive than zinc, electrolysis is usually used. The Extraction of Aluminium Aluminium is extracted from an ore called bauxite, which is impure aluminium oxide. Aluminium ions are attracted to the cathode and are reduced to aluminium: Al3+ + 3e- Al Oxide ions are attracted to the anode and lose electrons to form oxygen gas: 2O2- O2 + 4e- There are a few things to keep in mind: Melting aluminium requires extremely high temperatures. Instead, it is dissolved in an aluminium compound called cryolite. Because of high temperatures, the carbon anodes will burn with oxygen to form carbon dioxide. This means the anodes have to be replaced regularly. The cost of electricity is also a major factor – the cell has currents up to 100 000A so it is expensive. Uses of aluminium include: Use Property of Aluminium That This Useful
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