Question

discuss the importance of decomposition reaction in Metal Industries

Answer 1

Decomposition reaction is mainly useful in extracting pure metals from their ores 1. Thermal decomposition is used for the production of calcium oxide (quick lime) from calcium carbonate which is a major constituent of cement. Reaction Involved- CaCO3 (s) ? CaO (s) + CO2 (g) 2. Through electrolytic decomposition metals are extracted. Example sodium from sodium chloride. Molten sodium chloride on passing electricity is dissociated to sodium metal and chlorine gas. Reaction Involved- 2NaCl ? 2Na + Cl2 3. Aluminium is also electrolytically extracted from its ore bauxite (Al2O3). In the process crushed bauxite is treated with concentrated NaOH to form sodium tetrahydroxoaluminate. Reaction Involved- Al¬2O3 (impure) + 2H2O + 3H2O ? 2NaAl(OH)4 Impurities do not react with sodium hydroxide and are separated through filtration. Tetrahydroxoaluminate is cooled and seeded with previously formed aluminium hydroxide. NaAl(OH)4 ? Al(OH)3 + NaOH Pure aluminium oxide is made by heating aluminium hydroxide to temperature 1100 to 1200? C. 2Al(OH)3 ? Al¬2O3 + 3H2O This pure aluminium oxide is then decomposed elecrtolytically to obtain aluminium metal which is used in air crafts, utensils, power cables etc.