Make up the equations o f the reactions
ZnS + O2 =
HgS + O2 =
ZnO + C =
Zn + CdSO4 =
Zn + HNO3 (diluted) =
Hg + HNO3 (excess) =
Hg (excess) + HNO3 =
Zn + NaOH + H2O =
Cd + O2 =
Hg + O2 =
Hg(NO3)2 + NaOH =
Hg(NO3)2 + Hg =
Hg2(NO3)2 + NaCl =
Zn
+ OH
=
Cd(OH)2 + H =
Zn(OH)2 + OH =
Zn + NH3 =
HgCl2 + NH3 =
Hg(NO3)2 + KI =
Experimental section
1. Materials and equipment: metallic zinc, solutions of hydrochloric acid, sodium hydroxide, zinc sulphate, cadmium sulphate, mercury (ІІ) chloride, mercury (ІІ) nitrate, mercury (II) nitrate, sodium sulphide, ammonia, potassium iodide, sodium chloride, chlorine water, hydrogen-sulphide water, concentrated hydrochloric acid, sulfuric acid, nitric acid, 100 mls beakers, test tubes, glass rods.
2. Chemical properties of zinc
2.1. Put 1 granule of metallic zinc into each of two test tubes and add 5-6 drops of 2М solution: of hydrochloric acid into the first, of sodium hydroxide into the other one. Cautiously heat the second test tube. What can you observe? Give the equations of the relevant reactions.
2.2. Place 3-4 drops of 0,5N zinc sulphate solution into each of two test tubes and cautiously add by drops 2 M sodium hydroxide solution until precipitate forms. Then add 5-6 drops of 2 M hydrochloric acid solution into the first test tube, and the same volume of 2М sodium hydroxide solution into the other one. What can you observe? Give the equations of the relevant reactions.
2.3. Place 2-3 drops of 0,5N zinc sulphate solution into a test tube and add 2-3 drops of 2М ammonia solution. What can you observe? Then add by drops 2 M ammonia solution until precipitate dissolves completely. Give the equations of the relevant reactions.
2.4. Put 3-4 drops of 0,5N zinc sulphate solution into a test tube and cautiously add by drops 2 M sodium hydroxide solution until precipitate forms and then dissolves. Then pass carbonic gas from a Kipp gas generator in this solution. What can you observe? Give the equations of the relevant reactions.
2.5. Place 3-4 drops of 0,5N zinc sulphate solution into each of two test tubes and add 3-4 drops: of hydrosulfuric acid solution solution into the first, of 0,5N sodium sulphide solution into the other one. What can you observe? Why do different amounts of precipitates form? Give the equations of the relevant reactions.
3. Chemical properties of cadmium
3.1. Measure the value рH of zinc sulphate and of cadmium sulphate solution with the help of the рH-meter. What can you observe? Explain the difference of рH values of zinc and cadmium salts solutions. Which of these salts are hydrolysed to the greater extent? Why? Give the equations of the hydrolysis in the molecular and ionic forms.
3.2. Place 3-4 drops of 0,5N cadmium sulphate solution into each of three test tubes and cautiously add by drops 2 M sodium hydroxide solution until precipitate forms. Then add 5-6 drops of 2 M solutions: of hydrochloric acid into the first test tube, of sodium hydroxide into the second, of ammonia into the third one. What can you observe? What is the difference in the chemical behaviour of zinc and cadmium hydroxides? Give the equations of the relevant reactions.