Activity 6.7 Investigate the colour of the salts and their solubility in water

CHEMISTRY FORM 4 KSSM
CHAPTER 6 ACID, BASE AND SALT
Activity 6.7 Investigate the colour of the salts and their solubility in water

1. CHAPTER 6 ACID, BASE AND SALT PREPARED BY : ESTHER ANNE ANAK RANDI

2. Chapter 6 Acid, Base and Salt 6.1 Role of water in showing acidic and alkaline properties. 6.2 pH value 6.3 Strength of acids and alkalis 6.4 Chemical properties of acids and alkalis 6.5 Concentration of aqueous solutions 6.6 Standard solution 6.7 Neutralisation 6.8 Salts, crystals and their uses in daily life 6.9 Preparation of salts 6.10 Effect of heat on salts 6.11 Qualitative analysis

3. M What are the ingredients used to bake a cake ?

4. M Can you identify the cations and anions that makes up the salts above? Copper (II) ions, Cu 2+ Iron(II) ions, Fe 2+ Manganese (II) ions, Mn 2+ ? ions ? ions

5. Qualitative Analysis to Identify Cations and Anions in Salts Qualitative analysis of a salt – a technique used to identify the cations and anions present in a salt by analysing its physical and chemical properties . Steps involved in Qualitative Analysis of Salt : Observation on the physical properties of the salt ( Colour , Solubility ) Effect of heat on the salt Test for anions and cations Confirmatory tests for cations and anions

6. 1. Observations of the Physical Properties of Salts Observing the physical properties of salts such as colour and solubility is the first step to make inferences on the possibility of the presence of cations and anions in the salt. For example, if you see a blue salt crystal, you can make an inference : For solubility test of salts, even though it does not confirm the identities of the ions present, it helps us narrow down the possible identities of the ions present The salt crystal is blue due to the presence of copper(II) ions, Cu 2+

7. Activity 6.7 Investigate the colour of the salts and their solubility in water Aim : To investigate the colour of the salts and their solubility in water. Materials : Solid ammonium nitrate, NH 4 NO 3 , solid potassium nitrate, KNO 3 , solid sodium chloride, NaCl, solid calcium carbonate, CaCO 3 , solid calcium nitrate, Ca(NO 3 ) 2 , solid magnesium sulphate, MgSO 4 , solid magnesium carbonate, MgCO 3 , solid zinc sulphate, ZnSO 4 , solid zinc chloride, ZnCl 2 , solid iron(II) sulphate, FeSO 4 , solid iron(III) chloride, FeCl 3 , solid lead(II) nitrate, Pb(NO 3 ) 2 , solid lead(II) chloride, PbCl 2 , solid lead(II) sulphate, PbSO 4 , solid copper(II) sulphate, CuSO 4 , solid copper(II) chloride, CuCl 2 , solid copper(II) nitrate, Cu(NO 3 ) 2 , solid copper(II) carbonate, CuCO 3 and distilled water Apparatus : Test tubes, test tube rack, glass rod, spatula and wash bottle

8. Activity 6.7 Investigate the colour of the salts and their solubility in water Procedures : 1. Observe and record the colour of each solid salt. 2. Put a little amount of the salt into a test tube. Fill the test tube with distilled water and stir the mixture. 3. Observe the solubility of the salt and the colour of the solution formed. 4. Record all observations in Table 6.11.

9. Activity 6.7 Investigate the colour of the salts and their solubility in water Results : Type of salt Colour of salt Solubility in water Colour of salt solution Yes No Ammonium nitrate, NH 4 NO 3 White / Colourless Potassium nitrate, KNO 3 White / Colourless Sodium chloride, NaCl White / Colourless Calcium carbonate, CaCO 3 White / Insoluble Calcium nitrate, Ca(NO 3 ) 2 White / Colourless Magnesium sulphate, MgSO 4 White / Colourless Magnesium carbonate, MgCO 3 White / Insoluble Zinc sulphate, ZnSO 4 White / Colourless Zinc chloride, ZnCl 2 White / Colourless

10. Activity 6.7 Investigate the colour of the salts and their solubility in water Results : Type of salt Colour of salt Solubility in water Colour of salt solution Yes No Iron(II) sulphate, FeSO 4 Light green / Light green Iron(III) chloride, FeCl 3 Brown / Brown Lead(II) nitrate, Pb(NO 3 ) 2 White / Colourless Lead(II) chloride, PbCl 2 White / Insoluble Lead(II) sulphate, PbSO 4 White / Insoluble Copper(II) sulphate, CuSO 4 Blue / Blue Copper(II) chloride, CuCl 2 Green / Blue Copper(II) nitrate, Cu(NO 3 ) 2 Blue / Blue Copper(II) carbonate, CuCO 3 Green / Insoluble

11. Activity 6.7 Investigate the colour of the salts and their solubility in water Interpreting data : Name solid salts that are coloured : Green Brown Blue White Name green salts that are : Insoluble in water Soluble in water to form a blue solution Soluble in water to form a light green solution

12. Activity 6.7 Investigate the colour of the salts and their solubility in water Interpreting data : Name solid salts that are coloured : Green Iron(II) sulphate, FeSO 4 , copper(II) carbonate, CuCO 3 , copper(II) chloride, CuCl 2 Brown Iron(III) chloride, FeCl 3 Blue Copper(II) sulphate, CuSO 4 , copper(II) nitrate, Cu(NO 3 ) 2 White Ammonium nitrate, NH 4 NO 3 , potassium nitrate, KNO 3 , sodium chloride, NaCl, calcium carbonate, CaCO 3 , calcium nitrate, Ca(NO 3 ) 2 , magnesium sulphate, MgSO 4 , magnesium carbonate, MgCO 3 , zinc sulphate, ZnSO 4 , zinc chloride, ZnCl 2 , lead(II) nitrate, Pb(NO 3 ) 2 , lead(II) chloride, PbCl 2 , lead(II) sulphate, PbSO 4

13. Activity 6.7 Investigate the colour of the salts and their solubility in water Interpreting data : 2. Name green salts that are : Insoluble in water Copper(II) carbonate, CuCO3 Soluble in water to form a blue solution Copper(II) chloride, CuCl2 Soluble in water to form a light green solution Iron(II) sulphate, FeSO4

14. Activity 6.7 Investigate the colour of the salts and their solubility in water Discussion : Is the colour of the salt suitable to identify the cation presents in the salt? Explain. What is the colour of the solution formed when the white salt dissolves in water? Classify each salt as soluble salts or insoluble salts. What is the operational definition of insoluble salts ?

15. Activity 6.7 Investigate the colour of the salts and their solubility in water Discussion : Is the colour of the salt suitable to identify the cation presents in the salt? Explain. No. There are many various salts with the same colour .

16. Activity 6.7 Investigate the colour of the salts and their solubility in water Discussion : 2. What is the colour of the solution formed when the white salt dissolves in water? Colourless

17. Activity 6.7 Investigate the colour of the salts and their solubility in water Discussion : 3. Classify each salt as soluble salts or insoluble salts. Soluble salts : Iron(II) sulphate, FeSO 4 , copper(II) chloride, CuCl 2 , Iron(III) chloride, FeCl 3 , copper(II) sulphate, CuSO 4 , copper(II) nitrate, Cu(NO 3 ) 2 , ammonium nitrate, NH 4 NO 3 , potassium nitrate, KNO 3 , sodium chloride, NaCl, calcium nitrate, Ca(NO 3 ) 2 , magnesium sulphate, MgSO 4 , zinc sulphate, ZnSO 4 , zinc chloride, ZnCl 2 , lead(II) nitrate, Pb(NO 3 ) 2 Insoluble salts : calcium carbonate, CaCO 3 , magnesium carbonate, MgCO 3 , lead(II) chloride, PbCl 2 , lead(II) sulphate, PbSO 4 , copper(II) carbonate, CuCO 3

18. Activity 6.7 Investigate the colour of the salts and their solubility in water Discussion : 4. What is the operational definition of insoluble salts ? The salt that remains as solid in distilled water after the salt is put in a test tube containing distilled water.

19. Activity 6.7 Investigate the colour of the salts and their solubility in water All white soluble salts dissolve in water to form colourless salt solutions. Salts form coloured solutions due to the presence of ions in transition elements. For examples :

20. Activity 6.7 Investigate the colour of the salts and their solubility in water Table 6.12 shows the colour of some salts in the solid state and in aqueous solution.

21. Activity 6.7 Investigate the colour of the salts and their solubility in water Figure 6.49 shows the example on the qualitative analysis of a solid X which is green in colour and three possible results.