4. 1. Position of Hydrogen in periodic table
2. Isotopes of hydrogen
3. Methods of preparation, properties and
uses of dihydrogen.
4. Hydrides
5. Water — physical and chemical properties
6. Hardness of water and methods to remove it.
7. Heavy water
5. 9. preparation, properties and uses of
hydrogen peroxide.
10.Hydrogen economy
11.Uses of hydrogen as a fuel
12.Hydrazone
7. • In modern periodic table it is located
in first group.
Alkali metals Halogens
• lightest element known having
atomic number 1.
• Dihydrogen
• The position of hydrogen is
anomalous in periodic table
9. Both contain one electron less than
the nearest noble gas configuration
1
1 2
2 2 5
9 8
2 2 6 2 5
17 18
H 1s near to He
F 1s , 2s , 2p near to Ne
Cl 1s , 2s , 2p , 3s , 3p near to Ar
Typical non-metals.
Diatomic molecules.
1. Electronic configuration:
2. Non-metallic character:
3. Atomicity:
10. i. Halides: CCl4, SiCl4, GeCl4
ii. Hydrides: CH4, SiH4, GeH4
5. Oxidation state: –1
1 1 1 1
Na H Na Cl
11.
12. –
electrolysis
2 2 2H / OH
2H O 2H O
2. By partial oxidation of hydrocarbons
1. Electrolysis of water
2 3
673 K
2 2 2
Fe O
CO H O CO H
13. 2 3
673 K
2 2 2
Fe O
CO H O CO H
3. Water gas shift reaction
14. 1025 - 1075 K
2 (g)3Fe 4H O 3 4 2Fe O 4H
(2) Reduction stage
3 4 2 2 2
water gas
Fe O 2H CO 3Fe 2H O CO
(1) Oxidation stage
15.
2 3 2 3
2
Fe O / Cr O
steam, 770 K
CO H
Cold water
2 2 underpressure
Re d hot coke steam water gas
CO H
CO2 dissolves + H2 is collected
1270 K
2 (g) 2
Water gas
C H O CO H
2 3 2 3Fe O / Cr O
2 2 2 2
770 K
SteamWater gas
CO H H O CO 2H
16. Zn + dil H2SO4 ZnSO4 + 2H2O + SO2
Chemical properties:-
Not very reactive due to high bond dissociation
energy (435.88 kJ mol-1 at 298.2 K)
17. Can we use concentrated sulphuric acid and pure
zinc in the preparation of dihydrogen?
2 4 4 2Zn dil. H SO ZnSO H
(a) Conc. H2SO4 cannot be used because it acts as
oxidizing agent also and gets reduced to SO2.
2 4 4 2 2Zn 2H SO (conc.) ZnSO 2H O SO
(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.
18. (i) Combustion:- It burns with pale blue flame
2H2 (g) + O2 (g) 2H2O(l)
673 K, 200 atm
Fe
3H2 (g) + N2 (g) 2NH3 (g)
(ii) Reaction with nitrogen
(iii) Reaction with oxygen
970 K
2(g) 2(g) 2 (g)2H O 2H O
19. Reactive metals like Na, K, Ca, Li
525 K
2 2Ca H CaH
Metals like Pt, Pd, Ni form interstitial hydrides by
absorbing large volume of hydrogen. Such hydrogen
is called ‘occluded hydrogen’
(iv) Reaction with metals
Hydrogen reduces oxides of less active
metals to corresponding metal
Δ
3 4 2 2Fe O + 4H 3Fe + 4H O
2 2CuO H Cu H O
(v) Reaction with metal oxides:-
20. At room
temp.
75% 25%
stability more stable less stable
•Different physical properties
•Similar chemical properties.
Ortho hydrogen Para hydrogen
21. 3270 K
2(g) (g)
Atomic hydrogen
H 2H H 435.9 kJ
• Highly reactive.
• Half life period is 0.3 sec.
• 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.
Nascent hydrogen
24. Contains dissolved salts of bicarbonates,
sulphates and chlorides of calcium and
magnesium.
Hard water does not produce lather
with soap solution.
Soft water is free from bicarbonates,
sulphates and chlorides of calcium and
magnisum. It produce lather with soap
solution easily.
Soft water
e.g., distilled water, rain water
25. • due to presence of soluble bicarbonates of
calcium and magnesium.
• can be removed by simple boiling.
The hardness of water is of two types
(i)Temporary hardness
• due to presence of chlorides and sulphates of
calcium and magnesium.
• requires treatment of water to remove this type
hardness.
(ii)Permanent hardness
26. • Temporary hardness is also called carbonate
hardness
• Permanent hardness is also called non-carbonate
hardness
27. The process of removal of Ca2+
and Mg2+ ions from water is
called softening of water.
3 3 2 22
insolubleSoluble
(i) M HCO MCO H O CO
(M = Ca or Mg)
Removal of temporary hardness:-
Clark’s method or calcium hydroxide method
3 2 3 22
insolubleSoluble
Ca HCO Ca(OH) 2CaCO 2H O
3 2 3 222
insoluble insolubleSoluble
Mg HCO 2Ca(OH) 2CaCO Mg OH 2H
28.
2 2 3 3
insoluble
CaCl Na CO CaCO 2NaCl
4 2 3 3 2 4
insoluble
MgSO Na CO MgCO Na SO
(i) By washing soda (Na2CO3.10H2O)
treatment
29. ii)By using inorganic cation exchanger
(permutit method or Zeolite method):
2 2 2 8 2 2 2 8 2
Zeolite settles atbottom
Na Al Si O CaCl Ca Al Si O 2NaCl
The zeolite can be regenerated by
treatment with sodium chloride
solution.
2 2 8 2 2 2 8 22
Ca Al Si O 2NaCl Na Al Si O CaCl
30. (iii) By organic ion exchanger:
2
2
In hard water Cation exchanger
Mg 2H re sin Mg (resin) 2H
2
2
Hard water Cation exchanger
Ca 2H re sin Ca (resin) 2H
Cation exchanger
31.
2
4 4 2
Anion exchangerHard water
SO 2HO resin SO resin 2OH
Hard water Anion exchanger
Cl HO resin Cl re sin OH
22 Re generated resin
Exchausted resin
Ca resin 2HCl 2H re sin CaCl
Exchausted resin Re generated resin
Cl re sin NaOH HO re sin NaCl
32.
2 2 2 4 2 4 2 2
20% ice cooled 30% solution
solution
1. Na O H SO Na SO H O
2. From Barium peroxide
2 2 2 4 4 2 2 2BaO .8H O H SO BaSO 8H O H O
Barium sulphate is filtered off leaving behind H2O2.
Methods of preparation
33. electrolysis
H2SO4
4H HSO
At cathode
22H 2e H
At Anode 4 2 2 8
Peroxydisulphuric acid
2HSO H S O 2e
distilled
2 2 8 2 2 2 2 4
at reduced pressure
H S O 2H O H O 2H SO
H2O2 distills first leaving behind the H2SO4
which is recycled.
34. The H2O2 obtained by this method is further
concentrated by distillation under reduced pressure.
OH
OH
C2H5
2-ethyl anthraquinol
O
O
C2
H5
2-ethyl anthraquinone
air (O2)
35. 4 2 4 2 2 2 4 3 2(i) 2FeSO H SO H O Fe (SO ) 2H O
2 3 2 2 2 4 2(ii) H SO H O H SO H O
2 2 4 2
Black White
(iii) PbS 4H O PbSO 4H O
36. 4 6 2 4 2 2(iv) 2K Fe(CN) H SO H O
6 6 2 2 6 5 2
Phenol
(v) C H H O C H OH H
2 2 2 3 2(vii) NaNO H O NaNO H O
2 2 7 2 4 2 2 2 4 5 2(viii) K Cr O H SO 4H O K SO CrO 5H O
3 6 2 2 42K Fe(CN) 2H O K SO
37. 2 2 3 2 2(i) H O O H O O
2 2 2 2 2 2(ii) Ag O H O 2Ag H O O
2 3 2 2 3 2 2 2(iii) PbO 2HNO H O Pb(NO ) 2H O O
38. 4 2 4 2 2(iv) 2KMnO 3H SO 5H O
2 2 2 2(v) Cl H O 2HCl O
4 2 2 2(vi) 6KAuCl 3H O 2Au 2KCl 6HCl 3O
2 4 4 2 2K SO 2MnSO 8H O 5O
39. It reacts with alkalies and decomposes
carbonates.
2 2 2 2 2H O 2NaOH Na O 2H O
2 2 2 3 2 2 2 2H O Na CO Na O H O CO
1. For bleaching silk, wool, hair and leather
2. As rocket fuel
3. Dilute solution is sold in name ‘perhydrol’
Uses of hydrogen peroxide
40. H2O2 is stored in the bottles lined with wax
because…
The rough glass surface causes the decomposition
of hydrogen peroxide.
41. 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 2 22H O 2H O O
2(2 + 32) gm 22.4L at N.T.P.
= 68 gm or 22400 cm3 at N.T.P.
2 2 222400 ml of O is liberated from = 68 gm of H O
42. 2
2 2
10 ml of O is liberated from=
68
10 gm of H O
22400
But 10 ml of O2 at N.T.P. are produced from 1 ml of
10 volume H2O2 solution.
2 2
2 2
1 ml of 10 volume H O solution contains =
68
10 gm of H O
22400
= 0.03035 gm
2 2100 ml of 10 volume H O solution contains
= 0.03035 × 100
= 3.035 gm
= 3.035%
43. 2 2 22H O 2H O O
Calculate the normality of
30 volume of H2O solution:
2(2 + 32) gm 22.4L
= 68 gm
22.4 L of O2 is produced from = 68 gm of H2O2
230 L of O is produced from =
2 2Strength of 20 volume H O solution = 91.07 gm/mL
2 2 2 22H O 2H O O
68 parts by weight 32 parts by weight
44. 32 parts by weight of oxygen is
obtained from = 68 parts by weight of H2O2
2 2
32 parts by weight of oxygen is obtained from =
68
68 parts by weight of H O 8 17
32
2 2Equivalent weight of H O = 17
Strength 91.07
Normality 5.35
Equivalent weight 17
46. Calculate the normality of 30 volume
of H2O solution:
Solution:
2 2 22H O 2H O O
2(2 + 32) gm 22.4 L
= 68 gm
22.4 L of O2 is produced from = 68 gm of H2O2
68
30 gm
22.4
= 91.07 gm/mLStrength of 20 volume H2O2 solution
230 L of O is produced from
47. 2 2 2 22H O 2H O O
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 =
68
8 17
32
Strength 91.07
Normality 5.35
Equivalent weight 17
2 2Equivalent weight of H O = 17
48. • 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.
49. 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
50. • 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.
51. 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.
Transportation:
Hydrogen gas is explosive and hence it is
difficult to store and transport.
Formation of hydrogen from H2O:
