Make up the equations o f the reactionss
Br
+ Cl2
=
Br2 + H2 =
KI + I2 =
PI3 + H2O =
HBr + H2SO4 =
KBr + H2SO4 =
HI + H2SO4 =
NaI + H2SO4 =
I2 + H2O =
Br2 + Cl2 + H2O =
Br2 + NaOH
HBrO
HIO =
HIO3
KIO3 + Cl2 + KOH =
H5IO6
Experimental section
1. Materials and equipment: zinc dust, aluminium dust, magnesium dust, crystalline iodine, potassium iodide, potassium bromide, solutions of sulfuric acid, potassium iodide , potassium bromide, potassium chloride, silver nitrate, sodium hydroxide, potassium permanganate, potassium bromate, potassium iodate, chlorine water, bromine water, iodine water, benzol, benzine, ethanol, hydrogen peroxide, 100 mls flask, 100 mls beaker, test tubes, glass rods, microspatula.
2. 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.
Laboratory work 7
SULFUR
Themes for home preparation
Structure of atom, valence, oxidation state. Occurence in nature, obtaining. Physical and chemical properties.
Hydrogen sulphide, obtaining, structure of molecule. Acid-base properties. Sulphides, classification by solubility, hydrolysis. Reducing properties of hydrogen sulphide and sulphides.
Polysulphides, obtaining, structure and properties.
Sulfur (IV) oxide obtaining and properties. A sulfurous acid, its stability, acid-base properties, sulphites. Oxidation-reduction properties of sulfur (IV) oxide Hydrosulfurous acid and pyrosulfurous (disulfurous) acid, their salts.
Sulfur (VI) oxide obtainings and properties. Action of concentrated and diluted sulfuric acid on metals. Obtaining of sulfuric acid and its properties. Sulphates. Disulfuric (polysulfuric) acid, its properties. Peroxyacids of sulfur (peroxymonosulfuric and peroxydisulfuric), their obtaining, structure of molecules, properties.
Sodium thiosulphate, its obtaining, structure, properties. Polythionic acids, their salts.
Oxychlorides of sulfur (thionyl chloride, sulfuryl chloride), chlorosulphonic acid. Obtaining, structure of molecules, properties. Compounds with halogens.
Questions and tasks
1. What oxidation states are characteristic for chalkogenes in their compounds? Why do chalkogenes can show a maximum valency of 6, and oxygen is only 2?
2. What are the peculiarities of free sulfur structure? What molecules does solid, liquid and gaseous sulfur consist of? How does their composition depend on temperature?
3. How does sulfur react with water, acids and alkalies? Give the equations of the relevant reactions.
4. Give examples of reactions, in which sulfur acts as an oxidising agent, reducing agent, or participete in autoxidation - autoreduction.
5. Explain, using the concept of hybridization, how and why do the angles between bonds in molecules H2O (104,5°), H2S (92°), H2Se (91°), H2Te (89,5 °) change.
6. Analyze conditions of metals sulphides formation by double replacement reactions with H2S. Is it possible to receive in this way sulphides of a) Fe; b) Cd; c) Mn; d) Pb? What is the key difference of sulphides obtaining by double replacement reactions with H2S and Na2S?
7. How and why does the hydrolysis of sulphides proceeds? Is it possible to obtain sulphides Al2S3 and Cr2S3 by double replacement reactions in water solution? How and why do the products form?
8. What are polysulphides and sulphanes? How can they be received? Give the structure formula of H2S5 and indicate the oxidation states of sulfur in this compound.
9. How can sulfurous gas be received in industry and in laboratory? Where is sulfurous gas used?
10. What volumes of H2S and SO2 should react at standard conditions, to form 100 kgs of sulfur?
11. How is sulfuric acid received in industry? Why is free anhydride absorbed by sulfuric acid, not by water at its production? Are new compounds formed?
12. How does sulfuric acid react with metals and non-metals? Give the equations of the reactions of diluted and concentrated sulfuric acid interaction with magnesium, iron, copper, sulfur and carbon.
13. What reactions proceed at heating of hydrosulphite and hydrosulphate of sodium? Give the structural formulas of acids, which correspond to products of the reactions.
14. How are peroxydisulfuric and peroxymonosulfuric acid received? Give their structural formulas; indicate oxidation states of sulfur and oxygen.
15. What is the peculiarity of thiosulphate ion? Describe its oxidation-reduction properties. Give the equations of the relevant reactions.
16. What are polythionic acids? What composition and structure do they have? What oxidation states do atoms of sulfur have in these compounds? How is the tetrathionate of sodium received?
17. What compounds of sulfur with chlorine exist? What chemical properties do they have, how do they react with water, alkalis?