Chemical properties of fluorine, chlorine and their compounds

2.1. Put 3-4 crystals of manganese (ІV) dioxide into a test tube, add 1 ml of concentrated hydrochloric acid and heat up (carry out the experiment in a ventilating hood). What is observed? Cover an aperture of the test tube with a paper strip, moistened with solution of potassium iodide. What is observed? Give the equations of the relevant reactions.

2.2. Put 3-4 crystals of potassium permanganate into a test tube, add 1 ml of concentrated hydrochloric acid and heat up (carry out the experiment in a ventilating hood). What is observed? What gas is evolving? How can it be proved? Give the equations of the relevant reactions.

2.3. Put 3-4 crystals of potassium dichromate into a test tube, add 1 ml of concentrated hydrochloric acid and heat up (carry out the experiment in a ventilating hood). What is observed? What gas is evolving? How can it be proved? Give the equations of the relevant reactions.

2.4. Cover a glass plate with a layer of lampwax at slight heating. After lampwax solidifies, draw or write something on a plate with a nail, scratching lampwax to glass. Moisten a picture with hydrofluoric acid. In 15-20 minutes wash out a plate and delete lampwax. What is observed? Give the equations of the relevant reactions.

2.5. Put 1 g of crystalline sodium chloride into a test tube, add 1-2 mls of concentrated sulfuric acid and cautiously heat up (carry out the experiment in a ventilating hood). Collect the evolving gas in a dry test tube by the method of air replacement. Then close the aperture of the test tube with collected gas by a finger, upturn the test tube, plunge it in exsiccator with water and take away the finger. What is observed? Why? Close the test tube under water with a finger again and take it out of water. What is formed in the test tube? How can it be proved? Give the equations of the relevant reactions.

2.6. Put 2-3 g of crystalline substances into three test tubes: sodium chloride into the first, ammonium chloride into the second, calcium chloride into the third one, add 3-4 drops of concentrated sulfuric acid and heat up slightly (carry out the experiment in a ventilating hood). What is observed? Put wet litmus paper into the apertures of the test tubes, not touching their walls. What is observed? Put a glass rod wetted with concentrated ammonia solution into the apertures of test tubes. What is observed? Give the equations of the relevant reactions.

2.7. Place 3-4 drops of 0,5N solution of sodium fluoride into each of two test tubes and add 1-2 drops of 0,5N solutions: of calcium chloride into the first, of lead acetate into the second one. What is observed? Make a conclusion on the solubility of obtained fluorides.

2.8. Put 2-3 crystals of ammonium - iron (ІІ) sulphate FeSO₄ (NH₄)₂SO₄·6H₂O (Mohr's salt) into a test tube and add 2-3 drops of distilled water. Shake the test tube, so that the crystals dissolve and add to a solution 2-4 drops of 1 M sodium hydroxide solution. Note the colour of a precipitate, which was formed. Add 3-5 drops of sodium hypochlorite solution to the test tube and shake the test tube. What is observed? How does the colour of the precipitate change? Why? Give the equations of the relevant reactions.

2.9. Put 3-4 crystals of dry calcium hypochlorite - chloride (bleaching or lime chloride) into a test tube, add 3-5 drops of 0,5N lead acetate solution and heat up slightly. What is observed? How and why does the colour change? Give the equations of the reaction.

2.10. Put 3-4 crystals into two test tubes: of potassium chlorate into the first, of potassium perchlorate into the second and add 7-8 drops of water. Are salts dissolving well? Then add 3-4 drops of 0,5N solution of potassium iodide and 3-4 drops of diluted sulfuric acid into each test tube. What is observed? Compare obtained results and explain them. Do the reactions take place in both cases? Why?

Laboratory work 6

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