IGCSE Practical: Investigating the Solubility of Compounds through Chemical Reactions

Keywords: IGCSE, prescribed practical, solubility, compounds, chemical reactions, precipitates, scientific principles, equipment, method, calculations, findings, conclusion, questions, answers

Introduction: Solubility is the ability of a substance to dissolve in a particular solvent. It is an important property of chemical compounds, and it can be used to predict the outcomes of chemical reactions. In this IGCSE prescribed practical, we will investigate the solubility of compounds through chemical reactions that produce precipitates. A precipitate is a solid substance that forms in a liquid solution. We will use a range of chemical tests to determine whether a compound is soluble or insoluble.

Equipment:

• Test tubes
• Test tube rack
• Dropper pipettes
• Stirring rods
• Chemicals:
  • Sodium chloride (NaCl)
  • Silver nitrate (AgNO₃)
  • Barium hydroxide (Ba(OH)₂)
  • Sodium carbonate (Na₂CO₃)
  • Calcium chloride (CaCl₂)
  • Lead nitrate (Pb(NO₃)₂)
  • Potassium chloride (KCl)
  • Hydrochloric acid (HCl)
  • Sulfuric acid 0.1 mol dm^-3 (H₂SO₄)
  • Distilled water

Method:

1. Label six test tubes as follows: A, B, C, D, E, F.
2. Add a small amount of each chemical to a separate test tube and slowly add 10ml to test if they dissolve.
3. Add 2 mL of sodium chloride solution to test tube A.
4. Add 2 mL of silver nitrate solution to test tube A.
5. Observe any changes in the solution, such as the formation of a precipitate.
6. Repeat steps 2-4 with test tube B using barium hydroxide solution instead of silver nitrate solution.
7. Repeat steps 2-4 with test tube C using sodium carbonate solution instead of silver nitrate solution.
8. Repeat steps 2-4 with test tube D using calcium chloride solution instead of silver nitrate solution.
9. Repeat steps 2-4 with test tube E using lead nitrate solution instead of silver nitrate solution.
10. Repeat steps 2-4 with test tube F using potassium chloride solution instead of silver nitrate solution.
11. Add 2ml of Barium hydroxide to a test tube and add a few drops of sulfuric acid.
12. To test for the solubility of each compound, add a few drops of hydrochloric acid to each test tube.
13. Observe any changes in the solution, such as the disappearance of a precipitate.

Calculations/Expected Findings: Based on the solubility rules, we can predict that the following compounds will produce a precipitate:

• Silver chloride (AgCl)
• Barium carbonate (BaCO3)
• Calcium carbonate (CaCO3)
• Lead chloride (PbCl2)

The following compounds are expected to remain soluble:

• Sodium chloride (NaCl)
• Potassium chloride (KCl)

Conclusion: The results of this experiment demonstrate the importance of solubility in predicting the outcomes of chemical reactions. By observing the formation of precipitates and testing for solubility, we can determine whether a compound is likely to react with another compound. This knowledge is useful in a range of scientific fields, including chemistry, biology, and environmental science.

	Nitrate (NO3‑)	Chloride (Cl–)	Sulphate (SO4 2-)	Carbonate (CO3 2-)	Hydroxide (OH–)
Ammonium	Soluble	Soluble	Soluble	Soluble	Soluble
Potassium	Soluble	Soluble	Soluble	Soluble	Soluble
Sodium	Soluble	Soluble	Soluble	Soluble	Soluble
Barium	Soluble	Soluble	Insoluble	Insoluble	Soluble
Calcium	Soluble	Soluble	Slightly soluble	Insoluble	Slightly soluble
Magnesium	Soluble	Soluble	Soluble	Insoluble	Insoluble
Aluminium	Soluble	Soluble	Soluble	Insoluble	Insoluble
Zinc	Soluble	Soluble	Soluble	Insoluble	Insoluble
Iron	Soluble	Soluble	Soluble	Insoluble	Insoluble
Lead	Soluble	Insoluble	Insoluble	Insoluble	Insoluble
Copper	Soluble	Soluble	Soluble	Insoluble	Insoluble
Silver	Soluble	Insoluble	Slightly insoluble	Insoluble	Insoluble

Questions:

1. What is solubility?
2. What is a precipitate?
3. What chemical tests can be used to determine solubility?
4. What compounds are expected to produce a precipitate in this experiment?
5. Why is solubility an important property of chemical compounds?

Answers:

1. Solubility is the ability of a substance to dissolve in a particular solvent.
2. A precipitate is a solid substance that forms in a liquid solution

3. Chemical tests that can be used to determine solubility include adding a solution of the compound to another solution containing a reactive compound to observe the formation of a precipitate, and adding a few drops of a strong acid to observe the solubility of the compound.
4. The compounds that are expected to produce a precipitate in this experiment are silver chloride, barium carbonate, calcium carbonate, and lead chloride.
5. Solubility is an important property of chemical compounds because it can be used to predict the outcomes of chemical reactions and is useful in a range of scientific fields.