New Topic

1. New Topic “Equilibria and the manufacture of some important chemicals” Don’t forget your homework which is due on Monday (Questions on pages

2. Today’s lesson • Discuss the idea of a simple reversible reaction, such as the hydration of anhydrous copper (II) sulphate or the effect of heat on aluminium chloride • Explain the concept of dynamic equilibrium • Predict the effects of changing the conditions (P and T) on reversible reactions

3. Chemical reactions – What to look for This is from year 7!

4. Chemical reactions – What to look for • There may be a change ofcolour

5. Chemical reactions – What to look for • There may be a gas given off (bubbles)

6. Chemical reactions – What to look for • There may be an energy change (gets hotter or colder)

7. Chemical reactions – What to look for • New substances are formed, and the change is usually difficult to reverse

8. Word equations Zinc + sulphur reactants

9. Word equations Zinc + sulphur zinc sulphide reactants product(s)

10. Chemical reactions – What to look for • New substances are formed, and the change is usually difficult to reverse

11. Reversible reactions

12. Reversible reactions Can you stick the sheet in and read it please?

13. Reversible reactions • A reversible reaction is a chemical reaction that can go both ways. Hydrated copper sulphate Anhydrous copper sulphate + water

14. Reversible reactions • A reversible reaction is a chemical reaction that can go both ways. Ammonium chloride Ammonia + hydrogen chloride NH4Cl(s) NH3(g) + HCl (g)

15. Reversible reactions It often results in an dynamic equilibrium mixture in which the forward and backward reactions occur at the same rate. CH3COOH (aq) H+(aq) + CH3COO-(aq)

16. le Chatelier's principle The position of equilibrium shifts to try to cancel out any changes you make

17. le Chatelier's principle The position of equilibrium shifts to try to cancel out any changes you make A + B C + D Increasing the concentration of A means more C and D are produced to counteract the change

18. le Chatelier's principle The position of equilibrium shifts to try to cancel out any changes you make A + B C + D + heat Heating the mixture means the equilibrium moves to the left to counteract the change.

19. le Chatelier's principle The position of equilibrium shifts to try to cancel out any changes you make A(g) + B(g) C(g) Compressing the mixture means the equilibrium moves to the right to counteract the change.

20. The Haber process Fritz Haber 1868-1934

21. The Haber process • Ammonia (NH3)is a very important chemical used to make fertilisers and explosives. Fritz Haber 1868-1934

22. The Haber process • Ammonia (NH3)is a very important chemical used to make fertilisers and explosives. • Before WW 1. Germany imported nitrogen compounds from Peru and Chile – supplies were running out and war would make imports impossible anyway Fritz Haber 1868-1934

23. The Haber process • Ammonia (NH3)is a very important chemical used to make fertilisers and explosives. • Before WW 1. Germany imported nitrogen compounds from Peru and Chile – supplies were running out and war would make imports impossible anyway • German scientists raced to find a way to use the nitrogen in air to make ammonia Fritz Haber 1868-1934

24. The Haber process • Ammonia (NH3)is a very important chemical used to make fertilisers and explosives. • Before WW 1. Germany imported nitrogen compounds from Peru and Chile – supplies were running out and war would make imports impossible anyway • German scientists raced to find a way to use the nitrogen in air to make ammonia • N2(g) + 3H2(g) 2NH3(g) Fritz Haber 1868-1934

25. Some more reading to understand my very important process!

26. Some more reading to understand my very important process! Do you like my glasses?

27. Let’s try a question on my Haber process (Question 3)

28. Uses of Ammonia The majority of ammonia is used for the manufacture of fertilisers, but there are other uses.

29. Fertiliser manufacture • Ammonia is sometimes pumped directly into the soil as a fertiliser but because it is a gas much of it may escape. • More usually some of the ammonia is reacted with oxygen to form nitric acid NH3 + 2O2 HNO3 + H2O • This nitric acid is then reacted with more ammonia to give solid ammonium nitrate HNO3 + NH3 NH4NO3

33. The effects of fertiliser In a group of 3 or 4 write the words ‘The effects of fertiliser’ in the middle of a piece of A3 paper. Around the outside write down all of the effects – good and bad - that fertilisers can have on the environment.

34. Effect of artificial fertilisers on farming They have made naturally infertile soils, suitable for agriculture. This has been significant in poorer parts of the World. They eliminate the need to allow fields to lie fallow and for crop rotation. This enhances the productivity of the land. They increase the yield of the crops produced. This has allowed more land to be set aside for nature conservation and recreation. Fertilisers

35. The environment and fertilisers if too much used, at the wrong time of year, during wet weather, excess excess contaminates underground drinking water supplies washed into rivers and lakes causes causes fertilisers applied to farm land Excessive growth of aquatic plants. The bacteria which live on dead plants thrive and use up the oxygen in the water. The lack of oxygen causes death of fish. This is called eutrophication. Harm to infants - called ‘blue baby’ syndrome

36. Growmore is a NPK fertiliser (7-7-7) containing about 7% nitrogen, 7% phosphorous and 7% potassium.

37. NPK fertilisers Nitrogen (N)- needed for proteins in leaves and stalks. Phosphorous (P) - speeds up growth of the roots and helps fruit to ripen. Potassium (K) - speeds up seed growth and improves resistance to disease.

38. A problem for Farmer Giles Farmer Giles has been accused of raising nitrate levels in local water by using too much fertiliser. Here are some suggestions from other locals. Are they good or bad? • Split the fertiliser over 3 applications instead of just one. • Use a more soluble fertiliser so that it gets into the plants more easily. • Check the weather forecast and avoid applying it before rain is due. • Grow a quick crop of legumes instead of using a nitrogen containing fertiliser. • Use fertiliser with larger particle size.

39. Answers • Three applications instead of just one – good Plants get time to take in each application. • More soluble fertiliser – bad It will dissolve in rain and wash into local drains. 3. Avoid applying it before rain is due – good This means it won’t dissolve in the rain and wash into drains. 4. Grow a quick crop of legumes – good But depends on timings of crops, etc. 5. Use fertiliser with larger particle size – good Using the same amount of fertiliser with larger particles is likely to lead to a slower dissolving into the ground, giving plants more time to absorb it.

40. 1 2 3 4 5 6 7 8 9 Summary crossword Across: 1 Acid formed by oxidation of ammonia 8 Alkali metal present in NPK fertilisers 9 metal used as a catalyst in the Haber process Down: 2 Reaction that can go backwards 3 Element essential for growth of roots 4 Causes nitrates to be formed from the gases in air. 5 About 4/5 of air are made of this gas. 6 Formed in the Haber Process 7 Nitrogen compounds present in good soil

41. Crossword answers Across: 1 Acid formed by oxidation of ammonia. - nitric 8 Alkali metal present in NPK fertilisers. - potassium (K) 9 metal used as a catalyst in the Haber process. iron Down: 2 Reaction that can go backwards. - reversible 3 Element essential for growth of roots. - phosphorus 4 Forms nitrates from the gases in air. - lightning 5 About 4/5 of air are made of this gas. - nitrogen 6 Formed in the Haber Process - ammonia 7 Nitrogen compounds present in good soil - nitrates

42. Manufacture of Nitric acid

43. Manufacture of Nitric acid • A platinum/rhodium catalyst is used to react ammonia with oxygen to produce nitrogen monoxide and water Ammonia + oxygen nitrogen monoxide + water

44. Manufacture of Nitric acid • The nitrogen monoxide is mixed with air to produce nitrogen dioxide nitrogen monoxide + oxygen nitrogen dioxide

45. Manufacture of Nitric acid • The nitrogen dioxide and more oxygen react with water to make nitric acid nitrogen dioxide + oxygen + water nitric acid

46. Which word equation is correct? • Carbon + oxygen  carbon dioxide + water • Hydrogen + oxygen  carbon dioxide • Magnesium + oxygen  magnesium oxide • Methane + oxygen  carbon dioxide

47. Which process results in reduction in nitrate levels in the soil? • Lightning • Growth of legumes • Animal excretion • Growth of leaves

48. Which substances are raw materials for the Haber Process? • Oxygen and hydrogen • Oxygen and nitrogen • Nitrogen and hydrogen • Nitrogen and oxygen

49. What are the conditions used in the Haber Process? • Iron catalyst, 200 atm pressure, around 450oC • Nickel catalyst, 200 atm pressure, around 450oC • Iron catalyst, 450 atm pressure, around 200oC • Nickel catalyst, 450 atm pressure, around 200oC

50. In the Haber process how is ammonia separated from unchanged reactants? • Filtering it • Distilling it • Using chromatography • Liquefying it