3. Chemical properties of silver

3.1. Place 2-3 drops of 0,5N silver nitrate solution and 3-4 drops of 1М sodium hydroxide solution into each of three test tubes. What can you observe? Then add 5-6 drops of 1 M solutions: of nitric acid into the first one, of sodium hydroxide into the second, of ammonia into the third one. What processes occur? Give the equations of the relevant reactions.

3.2. Place 2-3 drops of 0,5N silver nitrate solution into six test tubes and add 3-4 drops of 0,5N solutions: of potassium chloride into the first and into the second, of potassium bromide into the third and in the fourth, of potassium iodide in the fifth and in the sixth. What can you observe? Then add 5-6 drops of 1 M of ammonia solution into the first, third and fifth test tubes, and 5-6 drops of 0,5N sodium thiosulphate solution into the second, fourth and sixth ones. What can you observe? Give the equations of the relevant reactions. Write down the equations of the dissociation of obtained complexes and expressions of ionisation constants of complex ions.

3.3. Place 2-3 mls of 0,5N silver nitrate solution into a test tube and add by drops 0,5N ammonia solution, until the grey- brown precipitate, which was formed at the first moment after adding the ammonia solution, completely dissolves forming the transparent solution of complex salt. Add to obtained solution the same volume of 0,5 M glucose solution and heat up a test tube slightly. What can you observe? Give the equation of the reaction.

Laboratory work 18

ELEMENTS of ZINC SUBGROUP

Themes for home preparation

Structure of atoms and oxidation states of zinc, cadmium and mercury. Occurrence in nature, obtaining of metals, their properties, reactions with acids and alkalis. Oxides, hydroxides and salts of zinc, cadmium and mercury (II). Solubility of salts, hydrolysis, complexes. Amyde compounds of mercury. Compounds of mercury (I): calomel, peculiarities of the structure and of the dissociation of the salts.

Questions and tasks

1. How are zinc, cadmium, mercury received in industry? Which of these metals can be received in one stage? Give the equations of the relevant reactions.

2. What are amalgams? Are they chemical compounds?

3. How can the fact be explained, that zinc reacts with sulfur only when heated up, and mercury - at standard conditions, hough zinc is more active metal, than mercury?

4. What amount of technical zinc, which contains 96 % of zinc, and of 27,5% hydrochloric acid solution is necessary to obtain 1 ton of 45% zinc chloride solution?

5. How do the composition of products of mercury reaction with diluted nitric acid depend on relative amount of reagents? Give the equations of the relevant reactions.

6. Why are two oxidation states: + 2 and + 1 characteristic for mercury unlike for cadmium and zinc? What is the valence of mercury in the relevant compounds?

7. What is similar and different between elements of zinc subgroup in ability to a complex forming? What coordination numbers are characteristic for each of these elements? Give examples of coordinative compounds of zinc, cadmium and mercury.

8. How do mercury (II) and mercury (I) nitrates react with alkalis and ammonia. Give the equations of the relevant reactions.

9. What volume of sodium hydroxide solution with concentration of 2 mol/l is necessary to dissolve completely 9,9 g of zinc hydroxide?

10. How do the acid-base properties of oxides and hydroxides of zinc, cadmium and mercury change? Give the equations of the relevant reactions.

11. How do the composition and properties of zinc (II), cadmium (II) and mercury (II) ammonia complexes change? What is the mechanism of mercury (II) amydochloride formation?