Chemical properties of bromine, iodine and their compounds

2.1. Put 3-5 drops of solutions into three test tubes: of potassium bromide into the first, of potassium iodide in the two others. Add 2-4 drops of benzol or benzene to each test tube.

Add 2-4 drops of chlorine water into two test tubes with solutions of potassium bromide and iodide, add bromine water to the third test tube with solution of potassium iodide. Mix the contents of test tubes with glass rod, washing it out carefully with water and wiping with filter paper each time.

By colouring of benzene ring spot determine, what halogen has evolved in a free state in each test tube. Write down the equations of the reactions of mutual replacement of halogens and indicate an oxidising agent and reducing agent for each of them. How is the oxidising ability of halogens changing from chlorine to iodine? Compare this conclusion with values of standard electrode potentials.

2.2. Place 1 ml of water into a test tube, add 1 ml of benzol and add by drops bromine water, shaking up the test tube. What is observed? Make a conclusion about relative solubility of bromine in water and benzol.

2.3. Put 1-2 crystals of iodine into each of two test tubes and add: 5 mls of water into the first, 1-2 mls of ethanol into the other and mix thoroughly. What is observed? Make a conclusion about the relative solubility of iodine in water and ethanol.

Add 1 microspatula of crystalline potassium iodide into a test tube with crystals of iodine and water. What is observed? Why? Give the equation of the reaction.

2.4. Mix 1 microspatula of zinc (or aluminium) dust and 1 microspatula of the crushed crystalline iodine in a porcelain casserole (carry out the experiment in a ventilating hood). Then add to the mixture few drops of water by glass rod. What is observed? What role does water play in this reaction? Give the equations of the relevant reactions.

2.5. Put 3-5 drops of bromine water into a test tube, add some magnesium or zinc sawdust and mix with glass rod. What is observed? Give the equations of the relevant reactions.

2.6. Put 3-4 drops of 0,5N solutions into three test tubes: of potassium chloride into the first, of potassium bromide into the other, of potassium iodide into the third one. Add 1-2 drops of silver nitrate solution to each test tube until precipitate forms. Write down the equations of the relevant reactions and note the colour of silver halogenides precipitates.

2.7. Put 3-4 drops of 1 M sodium hydroxide solution into two test tubes and add 3-4 drops: of bromine water into the first, of iodine water into the other. What is observed? Give the equations of the relevant reactions.

2.8. Put 3-4 drops of potassium iodide solution into a test tube and add 1-2 drops of sulfuric acid solution. Add 1-2 drops of 3% hydrogen peroxide solution H₂О₂. What is observed? Write down the equations of the relevant reactions.

2.9. Put 3-4 drops of 0,5N potassium permanganate solution, 3-4 drops of diluted sulfuric acid into two test tubes and add 2-3 crystals: of potassium bromide into the first, of potassium iodide into the other. What is observed? What is the discolouration of the solution caused by? Give the equations of the relevant reactions.

2.10. Place 1-2 mls of 0,5N potassium iodide solution into a test tube and add chlorine water drop by drop, shaking well the test tube after each drop added. Observe the appearing, and then disappearing of dark - brown colouring of free iodine. What is the discolouration of the solution caused by? Give the equations of the relevant reactions.

2.11. Place 2-3 drops of 0,5N solution of potassium bromide and 1-2 drops of 1 M solution of sulfuric acid into a test tube. Mix with glass rod and add drop by drop 0,5N solution of potassium bromate. What is observed? What is the discolouration of the solution caused by? Give the equations of the reaction.

2.12. Place 2-3 drops of 0,5N solution of potassium iodide and 1-2 drops of 1 M solution of sulfuric acid into a test tube. Mix with glass rod and add drop by drop 0,5N solution of potassium iodate. What is observed? What is the discolouration of the solution caused by? Give the equations of the reaction.

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