1. Lesson 5 Learning Objectives: Describe the test for specific negative ions Explain how precipitation reactions can be used as the test for some ions

2. What is the test for the following substances? Hydrogen Carbon dioxide Ammonium ions

3. Testing for Hydroxide, Carbonate, Sulphate and Sulphite Ions 1. Universal Indicator – check pH 2. Add HCL. If a gas is produced, test it with: Universal Indicator paper Limewater 3. Add dilute HCL, then add barium chloride solution

4. Results Anion present Hydroxide ion,Carbonate ion Sulphite ion Sulphate ion effect on universal indicator effect of adding hydrochloric acid effect of adding barium chloride followed by hydrochloric acid

5. Practical – Testing for Chlorine, Bromine and Iodine APlace 2 cm of each of the halide ion solutions in three different test tubes. BAcidify each solution by adding a few drops of nitric acid solution. CAdd a few drops of silver nitrate solution to each test tube. DObserve what happens (note colours carefully). halide ionchloride ionbromide ioniodide ion effect of adding acidified silver nitrate solution

6. Chloride Iodide Bromide The samples to be tested are first acidified using dilute nitric acid, then silver nitrate solution is added. White precipitate of silver chloride Cream precipitate of silver bromide Yellow precipitate of silver iodide

7. A white precipitate shows the presence of chloride ions Ag + (aq) + Cl − (aq) → AgCl(s) A cream precipitate shows the presence of bromide ions Ag + (aq) + Br − (aq) → AgBr(s) A yellow precipitate shows the presence of iodide ions Ag + (aq) + I − (aq) → AgI(s)

8. Word equation: nitric acid+ magnesium carbonate  ______ + water+ carbon dioxide Balanced equation: 2HNO 3 + MgCO 3  _____+ ____+ CO 2 If nitric acid is added to magnesium carbonate (MgCO 3 ), effervescence occurs. The magnesium carbonate slowly dissolves, forming the salt magnesium nitrate, water and carbon dioxide gas.

9. 1.When barium chloride solution is added to lithium sulphite solution, a white precipitate of barium sulphite is formed, leaving a solution of lithium chloride. lithium sulphite + barium chloride  ________ + __________ Balanced equation: Li 2 SO 3 (aq)+ BaCl 2 (aq)  __________ +BaSO 3 (s) 2. When barium chloride solution is added to potassium sulphate solution, a white precipitate of barium sulphate is formed leaving a solution of potassium chloride. Write a word and balanced symbol equation