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Heat changes in chemical reactions

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Heat changes in chemical reactions

  1. 1. HEAT CHANGES IN CHEMICAL REACTIONS
  2. 2. <ul><li>The chemical reaction that results in heat produced is called an exothermic reaction. </li></ul><ul><li>Example- Dissolving sodium hydroxide in water. </li></ul>
  3. 3. <ul><li>Exothermic reaction accompanied by a rise in temperature of the surrounding. </li></ul>
  4. 4. <ul><li>The chemical reaction that absorbs heat from the surrounding is called an endothermic reaction . </li></ul><ul><li>Example- Dissolving ammonium chloride in water. </li></ul>
  5. 5. <ul><li>Endothermic reaction resulting a drop of the temperature of the surrounding. </li></ul>
  6. 6. <ul><li>Energy graph for an exothermic reaction </li></ul>
  7. 7. <ul><li>Energy graph for an endothermic reaction . </li></ul>
  8. 8. <ul><li>The change of energy level in a chemical reaction is denoted by the symbol </li></ul>
  9. 9. <ul><li>When the energy level of the product is higher than that of reactants , energy is absorbed. </li></ul><ul><li>The reaction is endothermic and </li></ul><ul><li>(+) ve. </li></ul>
  10. 10. <ul><li>When the energy level of the product is lower than the reactants, energy is released. </li></ul><ul><li>The reaction is exothermic and </li></ul><ul><li>(-) ve. </li></ul>
  11. 11. HEAT CHANGES IN INDUSTRIAL CHEMICAL REACTION <ul><li>If a reaction is exothermic and reversible, heating the process to a very high temperature would decrease the yield of the products. </li></ul><ul><li>Example- Production of ammonia </li></ul>
  12. 12. HABER PROCESS <ul><li>Production of ammonia </li></ul><ul><li>Nitrogen + Hydrogen Ammonia + Heat </li></ul><ul><li>Heat is given off. So a low temperature will give better yield. </li></ul><ul><li>But a low temperature will cause the reaction to proceed slowly. </li></ul><ul><li>A moderate temperature of 450-500 is used. </li></ul>
  13. 13. CONTACT PROCESS <ul><li>Production of sulphuric acid. </li></ul><ul><li>Sulphur dioxide + Oxygen Sulphurtrioxide + Heat </li></ul><ul><li>Heat is given off. So a low temperature will give better yield. </li></ul><ul><li>But a low temperature will cause the reaction to proceed slowly. </li></ul><ul><li>A moderate temperature of 400-500 is normally used. </li></ul>
  14. 15. <ul><li>The sulphur trioxide is passed into concentrated sulphuric acid to form oleum. </li></ul><ul><li>Sulphur trioxide + Con. Sulphuric acid Oleum </li></ul><ul><li>Oleum + Water Sulphuric acid </li></ul>
  15. 16. THE END

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