1. Chemistry

2. Hydrogen

3. What do you understand by word “Hydrogen” ?
Session opener
What do you understand by word “Hydrogen” ?
Hydrogen in Greek means
Water producer

4. Session Objectives

5. Session objective Position of Hydrogen in periodic table
Isotopes of hydrogen
Methods of preparation, properties and uses of dihydrogen.
Hydrides
Water — physical and chemical properties
Hardness of water and methods to remove it.
Heavy water

6. Session objective
9. preparation, properties and uses of hydrogen peroxide.
10.Hydrogen economy
11.Uses of hydrogen as a fuel
12.Hydrazone

7. Session opener
Hydrogen in Greek means “water producer”

8. Position of Hydrogen in Periodic Table
lightest element known having atomic number 1.
Dihydrogen
The position of hydrogen is anomalous in periodic table
Alkali metals
Halogens
In modern periodic table it is located in first group.

9. Resemblance with alkali metals
1. Electronic configuration
2. Electropositive character
H+, Na+, K+ etc.
3. Oxidation state: +1

10. Resemblance with halogens
1. Electronic configuration:
Both contain one electron less than the nearest noble gas configuration
2. Non-metallic character:
Typical non-metals.
3. Atomicity:
Diatomic molecules.

11. 4. Formation of similar types of compounds
i. Halides: CCl4, SiCl4, GeCl4
ii. Hydrides: CH4, SiH4, GeH4
5. Oxidation state: –1

12. Isotopes of hydrogen

13. Methods for commercial production of dihydrogen
1. Electrolysis of water
2. By partial oxidation of hydrocarbons

14. Methods for commercial production of dihydrogen
3. Water gas shift reaction

15. By Lane process
(1) Oxidation stage
(2) Reduction stage

16. Bosch process
CO2 dissolves + H2 is collected

17. Laboratory preparation of hydrogen
Zn + dil H2SO ZnSO4 + 2H2O + SO2
Chemical properties:- Not very reactive due to high bond dissociation energy ( kJ mol-1 at K)

18. Ask yourself?
Can we use concentrated sulphuric acid and pure zinc in the preparation of dihydrogen?
(a) Conc. H2SO4 cannot be used because it acts as oxidizing agent also and gets reduced to SO2.
(b) Pure Zn is not used because it is non-porous and reaction will be slow. The impurities in Zn help in constitute of electrochemical couple and speed up reaction.

19. Chemical properties (i) Combustion:- It burns with pale blue flame
2H2 (g) + O2 (g) H2O(l)
(ii) Reaction with nitrogen
3H2 (g) + N2 (g) NH3 (g)
(iii) Reaction with oxygen

20. Chemical properties (iv) Reaction with metals
Reactive metals like Na, K, Ca, Li
Metals like Pt, Pd, Ni form interstitial hydrides by absorbing large volume of hydrogen. Such hydrogen is called ‘occluded hydrogen’
(v) Reaction with metal oxides:-
Hydrogen reduces oxides of less active metals to corresponding metal

21. Ortho and para hydrogens
At room temp.
75%
25%
stability
less stable
more stable
Different physical properties
Similar chemical properties.

22. Atomic hydrogen Highly reactive. Half life period is 0.3 sec.
Nascent hydrogen
The hydrogen produced in contact with the substance to be reduced is known as ‘nascent hydrogen’.
It is very reactive form of hydrogen
Better reducing agent than ordinary dehydrogen.

23. Structure of water
Gaseous state
Solid state

24. Structure of ice

25. Hard water
Contains dissolved salts of bicarbonates, sulphates and chlorides of calcium and magnesium.
Hard water does not produce lather with soap solution.
Soft water
Soft water is free from bicarbonates, sulphates and chlorides of calcium and magnisum. It produce lather with soap solution easily.
e.g., distilled water, rain water

26. Types of hardness The hardness of water is of two types
(i)Temporary hardness
• due to presence of soluble bicarbonates of calcium and magnesium.
• can be removed by simple boiling.
(ii)Permanent hardness
• due to presence of chlorides and sulphates of calcium and magnesium.
• requires treatment of water to remove this type hardness.

27. Do you know? Temporary hardness is also called carbonate hardness
Permanent hardness is also called non-carbonate hardness

28. Softening of water
The process of removal of Ca2+ and Mg2+ ions from water is called softening of water.
Removal of temporary hardness:-
(M = Ca or Mg)
Clark’s method or calcium hydroxide method

29. Removal of permanent hardness
(i) By washing soda (Na2CO3.10H2O) treatment

30. Removal of permanent hardness
ii)By using inorganic cation exchanger (permutit method or Zeolite method):
The zeolite can be regenerated by treatment with sodium chloride solution.

31. Removal of permanent hardness
(iii) By organic ion exchanger:
Cation exchanger

32. Anion exchanger

33. Hydrogen peroxide Methods of preparation 2. From Barium peroxide
Barium sulphate is filtered off leaving behind H2O2.

34. 3. By electrolysis of 50% H2SO4
At cathode
At Anode
H2O2 distills first leaving behind the H2SO4 which is recycled.

35. 4. By auto oxidation of 2-ethylanthraquinol
The H2O2 obtained by this method is further concentrated by distillation under reduced pressure.

36. Oxidising properties

37. Oxidising properties

38. Reducing properties

39. Reducing properties

40. Acidic properties It reacts with alkalies and decomposes carbonates.
Uses of hydrogen peroxide
1. For bleaching silk, wool, hair and leather
2. As rocket fuel
3. Dilute solution is sold in name ‘perhydrol’

41. Do you know? H2O2 is stored in the bottles lined with wax because…
The rough glass surface causes the decomposition of hydrogen peroxide.

42. Volume strength of hydrogen peroxide (solved example 1)
Calculate the percentage strength of a 10 volume H2O2 solution.
10 volume hydrogen peroxide means that 1 ml of such a solution of hydrogen peroxide on heating will produce 10 ml of oxygen at N.T.P.
2(2 + 32) gm L at N.T.P.
= 68 gm or cm3 at N.T.P.

43. Solution
But 10 ml of O2 at N.T.P. are produced from 1 ml of 10 volume H2O2 solution.
= gm

44. Volume strength of hydrogen peroxide (solved example 2)
Calculate the normality of 30 volume of H2O solution:
2(2 + 32) gm L
= 68 gm
22.4 L of O2 is produced from = 68 gm of H2O2
68 parts by weight 32 parts by weight

45. Solution
32 parts by weight of oxygen is obtained from = 68 parts by weight of H2O2

46. Structure of hydrogen peroxide

47. Illustrative example
Calculate the normality of 30 volume of H2O solution:
Solution:
2(2 + 32) gm L = 68 gm
22.4 L of O2 is produced from = 68 gm of H2O2
= gm/mL

48. solution 68 parts by weight 32 parts by weight
32 parts by weight of oxygen is obtained from = 68 parts by weight of H2O2
parts by weight of oxygen is obtained from =

49. Heavy Water (D2O) Was discovered by Urey in 1932.
Ordinary water contains one part of heavy water in 600 parts of it.
Used as moderator in nuclear reactions.
Used as tracer in study of mechanism of physiological process.
Used in preparation of deuterium compounds.

50. Hydrogen economy (Hydrogen as fuel)
With advancement of science and technology we realise in order to make our lives comfortable fossil fuels are depleating at an alarming rate and will be exahausted soon. The electricity cannot be stored to run automobiles. It is not possible to store and transport nuclear energy. Hydrogen is another alternative source of energy and hence called as ‘hydrogen economy’. Hydrogen has some advantages as fuel

51. Hydrogen economy (Hydrogen as fuel)
Available in abundance in combined form as water.
On combustion produces H2O. Hence pollution free.
H2-O2 fuel cell give more power.
Excellent reducing agent. Therefore can be used as substitute of carbon in reduction for processes in industry.

52. Obstacles in hydrogen economy
Transportation:
Hydrogen gas is explosive and hence it is difficult to store and transport.
Formation of hydrogen from H2O:
The cheaper production of the hydrogen is basic requirement of hydrogen economy which is not possible now.
The main aim and advantage of hydrogen economy is to transmit energy in four of hydrogen.

53. Thank you