8. The change of energy level in a chemical reaction is denoted by the symbol
9. When the energy level of the product is higher than that of reactants , energy is absorbed. The reaction is endothermic and is (+) ve.
10. When the energy level of the product is lower than the reactants, energy is released. The reaction is exothermic and is (-) ve.
11. HEAT CHANGES IN INDUSTRIAL CHEMICAL REACTION If a reaction is exothermic and reversible, heating the process to a very high temperature would decrease the yield of the products. Example- Production of ammonia
12. HABER PROCESS Production of ammonia Nitrogen + Hydrogen Ammonia + Heat Heat is given off. So a low temperature will give better yield. But a low temperature will cause the reaction to proceed slowly. A moderate temperature of 450-500 is used.
13. CONTACT PROCESS Production of sulphuric acid. Sulphur dioxide + Oxygen Sulphurtrioxide + Heat Heat is given off. So a low temperature will give better yield. But a low temperature will cause the reaction to proceed slowly. A moderate temperature of 400-500 is normally used.
14. The sulphur trioxide is passed into concentrated sulphuric acid to form oleum. Sulphur trioxide + Con. Sulphuric acid Oleum Oleum + Water Sulphuric acid