Make up the equations o f the reactionss

TiO₂ + C + Cl₂ =

Ti + HCl =

Zr + HF =

Ti + C =

Zr + O₂ =

TiO₂ + H₂SO₄ =

TiO(OH)₂ + HCl =

TiOCl₂ + Zn + HCl =

TiCl₄ + Mg =

Ti + HF =

Zr + HF + HNO₃ =

Ti + N₂ =

TiO₂ + NaOH

TiOSO₄ + NaOH =

TiCl₄ + H₂O =

TiCl₃ + O₂ + H₂O =

Experimental section

1. Materials and equipment: titanium dust, metallic zinc, crystalline ammonium fluoride, solutions of hydrochloric acid, acetic acid, titanyl sulphate, titanyl chloride, sodium hydroxide, litmus, concentrated hydrochloric acid, 100 mls flask, 100 mls beakers, test tubes, glass rods, microspatula.

2. Chemical properties of titanium

2.1. Put 1 microspatula of titanium dust into a test tube and add 4-6 drops of concentrated hydrochloric acid. What can you observe? 2-3 minutes later heat up the test tube cautiously. Write down your observations and the equation of the reaction. What oxidation state does titanium have in compound formed?

2.2. Put 1 microspatula of titanium dust into a test tube and add 4-6 drops of diluted acetic acid. What can you observe? 2-3 minutes later add few crystals of ammonium fluoride. Write down your observations and the relevant equations of the reactions.

2.3. Place 2-3 drops of 0,5N titanyl sulphate solution into each of two test tubes and add 1-3 drops of diluted sodium hydroxide solution in each one until precipitate forms. To this precipitate add 3-5 drops of 2M solution: of hydrochloric acid into the first, of sodium hydroxide into the other. What can you observe? Give the equations of the relevant reactions and make a conclusion on acid-base properties of the obtained precipitate.

2.4. Place 2-3 drops of 0,5N titanyl sulphate solution into a test tube and add 2-3 drops of litmus neutral solution. What can you observe? Give the equations of the hydrolysis in the molecular and ionic forms.

2.5. Place 4-6 drops of 0,5N solution of titanyl chloride into a test tube, add 4-6 drops of concentrated hydrochloric acid and 2-3 granules of zinc. What can you observe? Give the equations of the relevant reactions and explain the discolouration of the solution.

Laboratory work 15

ELEMENTS of CHROME SUBGROUP

Themes for home preparation

General characteristic of elements: occuring in nature, obtaining, properties. Compounds of chromium (II) and (III). Oxides and hydroxides of chromium (II) and (III), methods of their obtaining, acid-base properties. Alum. Chromites.

Oxide of chromium (VI), its properties. Chromic acids, chromates, dichromates, their obtaining, properties and mutual transformations. Oxidising properties of chromium (VI) compounds. Compounds of molybdenum and tungsten. Acid-base properties of oxides and hydroxides. Molybdenic and tungstenic acids and their salts. Application of simple substances and compounds.

Questions and tasks

1. What is common and different in the structure of chalkogenes atoms and of chrome subgroup elements atoms? Why do the latter show properties of metals? Make the electron formulas of atoms of chrome, molybdenum and tungsten.

2. How are chrome subgroup metals received in industry? Give the equations of the relevant reactions.

3. How does chrome react with hydrochloric, sulfuric and nitric acids? Give the equations of the relevant reactions.

4. What occurs at mixing of water solutions of: а) Cr₂(SO₄)₃ and Na₂S б) Cr(NO₃)₃ and Na₂CO₃? Give the equations of the relevant reactions in the molecular and ionic - molecular forms and explain the mechanism of these transformations.

5. Why at action of silver nitrate on water solutions of three isomers with identical composition CrCl₃6H₂O are precipitated one, two or three moles of silver chloride on each mol of isomer respectively?

6. What anions of chrome (VI) exist in water solutions and at what conditions are possible their mutual transformations? Give the ionic - molecular equations of the relevant reactions.

7. A gas of 200 mls volume had evolved at action of 1 g of water solution of hydrogen peroxide with excess amount of potassium dichromate and sulfuric acid at the temperature of 27° and at pressure of 100 kPa. Calculate weight fraction of hydrogen peroxide in the solution.

8. How are molybdenic and tungstenic acids received?

9. How and why do the ability to polymerisation, solubility and acid-base properties in a range H₂CrO₄ - H₂MoO₄ - H₂WO₄ change?

10. How does the thermal decomposition of ammonium chromate, molybdate and tungstenate proceed? Give the equations of the relevant reactions and explain the peculiarities of their proceeding.