discuss the importance of decomposition reaction in Metal Industries with three points
Answers
1.Thermal decomposition is used for the production of calcium oxide (quick lime ) from calcium carbonate which is a major constituent of cement.
2. Rancidity can be prevented by adding antioxidants to food containing fat and oil, e.g. butylated hydroxy anisole is added to butter as antioxidant.
3. It can be prevented by packaging fat and oil containing foods in nitrogen gas.
4. Molten NaCl is electrolytically decomposed to form sodium metal.
5. Aluminium metal is obtained by electric decomposition of bauxite ore mixed with cryolite.
Answer:
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.