iGCSE chemistry Section 4 lesson 1

1. iGCSE chemistrySection 4 lesson 1

2. Content The iGCSE Chemistry course Section 1 Principles of Chemistry Section 2 Chemistry of the Elements Section 3 Organic Chemistry Section 4 Physical Chemistry Section 5 Chemistry in Society

3. Content Section 4 Physical Chemistry • Acids, alkalis and salts • Energetics • Rates of reaction • Equilibria

4. 4.1 describe the use of the indicators litmus, phenolphthalein and methyl orange to distinguish between acidic and alkaline solutions 4.2 understand how the pH scale, from 0–14, can be used to classify solutions as strongly acidic, weakly acidic, neutral, weakly alkaline or strongly alkaline 4.3 describe the use of universal indicator to measure the approximate pH value of a solution 4.4 define acids as sources of hydrogen ions, H+, and alkalis as sources of hydroxide ions, OH¯ 4.5 predict the products of reactions between dilute hydrochloric, nitric and sulfuric acids; and metals, metal oxides and metal carbonates (excluding the reactions between nitric acid and metals) 4.6 understand the general rules for predicting the solubility of salts in water: i all common sodium, potassium and ammonium salts are soluble ii all nitrates are soluble iii common chlorides are soluble, except silver chloride iv common sulfates are soluble, except those of barium and calcium v common carbonates are insoluble, except those of sodium, potassium and ammonium 4.7 describe experiments to prepare soluble salts from acids 4.8 describe experiments to prepare insoluble salts using precipitation reactions 4.9 describe experiments to carry out acid-alkali titrations. Lesson 1 a) Acids, alkalis and salts

5. pH scale and indicators The pH scale is a measure of how acidic or alkaline a solution is.

6. pH scale and indicators The pH scale is a measure of how acidic or alkaline a solution is.

7. pH scale and indicators The pH scale is a measure of how acidic or alkaline a solution is. A substance forms an aqueous solution when it dissolves in water. Water itself is neutral. When substances dissolve in water, they dissociate into individual ions.

8. pH scale and indicators Water, H2O H+(aq) OH-(aq) hydrogen ion hydroxide ion acid alkali

9. pH scale and indicators Indicators are special dyes that change colour according to whether they are in acidic, alkaline or neutral solutions.

10. pH scale and indicators Indicators are special dyes that change colour according to whether they are in acidic, alkaline or neutral solutions. Three common indicators are: Litmus Phenolphthalein Methyl Orange

11. pH scale and indicators Litmus 5.0 8.0

12. pH scale and indicators Methyl Orange 4.4 6.2

13. pH scale and indicators Phenolphthalein 8.3 10

14. pH scale and indicators Universal indicator is a mixture of dyes, and shows a complete colour range across the pH scale.

15. Common acids and alkalis ACIDS

16. Common acids and alkalis ACIDS ALKALIS

17. Salt formation When acids and alkalis react together, salts are formed. The general equation is: Acid + Base  Salt + Water

18. Salt formation When acids and alkalis react together, salts are formed. The general equation is: Acid + Base  Salt + Water This is known as a neutralisation reaction because the products are neutral.

19. Salt formation Salts consist of two parts – a metal part, and the non-metal ion from the acid.

20. Salt formation Examples of salts

21. Reactions of salts Acids + Metals Acid + Metal  Salt + Hydrogen

22. Reactions of salts Acids + Metals Acid + Metal  Salt + Hydrogen Magnesium + Hydrochloric  Magnesium + Hydrogen Acid chloride Mg + 2HCl  MgCl2 + H2

23. Reactions of salts Acids + Metals Have you got that? Are you really sure? Let’s try a few examples.

24. Reactions of salts Acids + Metals Magnesium + Sulphuric Acid  Iron + Hydrochloric Acid  Lead + Sulphuric Acid 

25. Reactions of salts Acids + Metals Magnesium + Sulphuric Acid  Magnesium sulphate + Hydrogen Iron + Hydrochloric Acid  Iron chloride + Hydrogen Lead + Sulphuric Acid  Lead sulphate + Hydrogen

26. Reactions of salts Acids + Metal oxides Acid + Metal oxide  Salt + Water

27. Reactions of salts Acids + Metal oxides Acid + Metal oxide  Salt + Water Copper + Sulphuric  Copper + Water oxide Acid sulphate CuO + H2SO4 CuSO4+ H2O

28. Reactions of salts Acids + Metal oxides Have you got that? Are you really, really sure? Let’s try a few more examples.

29. Reactions of salts Acids + Metal oxide Magnesium + Hydrochloric Acid  oxide Iron + Sulphuric Acid  oxide Lead + Hydrochloric Acid  oxide

30. Reactions of salts Acids + Metal oxide Magnesium + Hydrochloric Acid  Magnesium + Water oxide chloride Iron + Sulphuric Acid  Iron sulphate + Water oxide Lead + Hydrochloric Acid  Lead chloride + Water oxide

31. Reactions of salts Acids + Metal carbonate Acid + Metal  Salt + Carbon + Water carbonate dioxide

32. Reactions of salts Acids + Metal carbonate Acid + Metal  Salt + Carbon + Water carbonate dioxide Copper + Hydrochloric  Copper + Carbon + Water Carbonate acid chloride dioxide CuCO3 + 2HCl  CuCl2 + CO2 + H2O

33. Reactions of salts Acids + Metal carbonate Guess what? That’s right, no more examples!

34. Solubility of salts If a substance is soluble, then this means that it will dissolve in a solvent.

35. Solubility of salts If a substance is soluble, then this means that it will dissolve in a solvent. The most common solvent you will come across is WATER.

36. Solubility of salts If a substance is soluble, then this means that it will dissolve in a solvent. The most common solvent you will come across is WATER. Solute (the solid) + Solvent (water)  Solution (aqueous)

37. Solubility of salts There’s no easy way around this – you’ve just got to learn the relative solubility of salts!

38. Solubility of salts All ammonium, potassium and sodium salts are soluble in water.

39. Solubility of salts All ammonium, potassium and sodium salts are soluble in water. All nitrates are soluble in water

40. Solubility of salts All ammonium, potassium and sodium salts are soluble in water. Most chlorides are soluble in water (except lead and silver). PbCl2 is soluble in hot water. All nitrates are soluble in water

41. Solubility of salts All ammonium, potassium and sodium salts are soluble in water. Most sulphates are soluble in water (except barium, calcium and lead) Most chlorides are soluble in water (except lead and silver). PbCl2 is soluble in hot water. All nitrates are soluble in water

42. Solubility of salts Most carbonates are insoluble in water (except sodium, potassium and ammonium) All ammonium, potassium and sodium salts are soluble in water. Most sulphates are soluble in water (except barium, calcium and lead) Most chlorides are soluble in water (except lead and silver). PbCl2 is soluble in hot water. All nitrates are soluble in water

43. Preparing insoluble salts using precipitation reactions Preparing soluble salts from acids Carrying out acid-alkali titrations

44. Preparing soluble salts from acids Eg. the preparation of sodium chloride by neutralization

45. Preparing soluble salts from acids Eg. the preparation of sodium chloride by neutralization Dilute sodium hydroxide + indicator solution Dilute hydrochloric acid

46. Preparing soluble salts from acids Eg. the preparation of sodium chloride by neutralization Filtrate Decolourising charcoal Evaporating basin

47. Preparing soluble salts from acids Eg. the preparation of sodium chloride by neutralization Crystals of sodium chloride forming) Acid + Alkali  Salt + Water Filtrate Steam HCl(aq) + NaOH(aq) NaCl(aq) + Water(l) Water bath Bunsen burner

48. Preparing insoluble salts using precipitation reactions Eg. the preparation of lead iodide

49. Preparing insoluble salts using precipitation reactions Eg. the preparation of lead iodide Yellow precipitate of lead iodide Lead nitrate Potassium iodide

50. Preparing insoluble salts using precipitation reactions Eg. the preparation of lead iodide Filter to separate the precipitate. Wash with distilled water and dry to get the pure product. Lead iodide