Why are hydrogen and carbon reducing agents

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1 Chapter name 7 The transformation of substances by humans 92 7.6 Metals are obtained through redox reactions The production of metals is based on ores. These are metal compounds with such a large proportion of metal that it is economically worthwhile to dismantle them. The most important ores are metal oxides. The task is therefore to remove the oxygen from the metal oxide. This reaction is called reduction. It is the reverse of the oxidation. Melting alone is not enough. If you melt a metal oxide, you don't get the metal, but the liquid metal oxide. One is therefore looking for another substance that removes oxygen from the metal oxide. This substance is called a reducing agent. The reducing agent is oxidized during the reaction. This is why the entire process is called a redox reaction, since a reduction is always coupled with an oxidation. In experiment 93.1 we reduce copper oxide with iron powder. The iron powder is the reducing agent. It is oxidized to iron oxide. The copper oxide is reduced to copper. The resulting copper has no longer bound any oxygen. The reaction is exothermic. We saw this with the glow. The heating was only used to start the reaction. Oxidation is the uptake of oxygen, reduction is the release of oxygen. Reducing agents take up oxygen. In metal production, you need reducing agents that are as strong and cheap as possible. Carbon is used very often. In experiment 93.2 we use charcoal, in the technology coke is used. It is obtained from the relatively cheap coal. To obtain coke, the coal is heated for several hours in the absence of air. As a result, the organic compounds are dissolved out of the coal as gas and tar and a porous carbon skeleton remains, the coke. Another important reducing agent is carbon monoxide. It is produced when coke is burned in the absence of air at high temperatures. Iron is obtained with this reducing agent. Metals that react with carbon cannot be made this way. Here you have to use more expensive reducing agents, such as hydrogen or aluminum. Tungsten oxide is reduced with hydrogen, chromium oxide with aluminum. No suitable reducing agents can be found for the production of metals, which are themselves particularly good reducing agents. They have to be made by electrolysis of their molten salts. Aluminum and magnesium are produced in this way, but also the alkali metals (1st main group of the PSE). Fig. 92.1: Reduction of copper oxide to copper Fig. 92.2: Production of coke from hard coal and the resulting by-products Fig. 92.3: The most important reducing agents for metal extraction 3 CuO + 2 Fe 3 Cu + Fe 2 O 3 Reduction Oxidation Oxygen release Oxygen absorption Oxygen from . Oxygen on. Copper oxide gives iron takes hard coal COKS tar coal gas heating carbon as coal or coke carbon monoxide as gas hydrogen gaseous aluminum only for test purposes - property of the publisher öbv

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