Hydrogen 2017

Hydrogen is Diatomic [H2] Why?
1. Hydrogen having one electron in its
valence shell (E.C-1s1).
2. to attain stability, hydrogen has to have
two electrons so that it can complete it's
duplet.
3. therefore, it shares its single electron
with other H-atom to achieve stable inert
gas configuration of He.

Also called
β-emitter
rays.
Half life 12.33years.

Making
water
solution
electrolyte.
H
liberated
O
liberated
H+ = HCl etc
During
electrolyte
following
reaction take
place.
This method use
in water (water is
poor conductor).
Acidified water.

Syngas
1. mixture of CO and H2. also called ‘water gas’.
2. used for preparation of methanol and many
hydrocarbons, also called syngas or ‘synthesis
gas’.
3. produced from saw dust or scrap wood.
4. The process of producing syngas from coal or
coke is called ‘coal gasification’.
CO(g) + 2H2(g) ⎯⎯⎯→ CH3 − OH(l)
Syngas Methanol
(water gas)
Cobalt catalyst

Syngas
1. The process of producing syngas from coal or
coke is called ‘coal gasification’.
CO(g) + 2H2(g) ⎯⎯⎯→ CH3 − OH(l)
Syngas Methanol
(water gas)
Cobalt catalyst
2. Syngas is also used to prepare hydrogen.
CO + H2 + H2O ⎯⎯⎯⎯⎯→ CO2(g) ↑ + 2H2(g)
(Water gas) Steam
Fe2O3 + Cr2O3
773K

Water gas shift reaction
1. Since it is difficult to remove carbon
monoxide from the water gas (syngas),
obtaining hydrogen from water gas
(syngas) also becomes difficult.
2. water gas is mixed with steam and
heated at 673 K in the presence of iron
chromate (FeCrO4) catalyst.
CO(g) + H2O(g) ⎯⎯⎯→ CO2(g) + H2(g)
FeCrO4
673 K
sodium arsenite solution remove CO2 by scrubbing

Chemical reactivity of dihydrogen
1. Chemical reaction take place when H-H
bond break.
2. The bond dissociation(Break)
enthalpy(energy) of H−H bond is very high
(435.88 kJmol−1 at 298 K).
3. Due to high bond enthalpy, not reactive at
R.T.
4. at high T or presence of catalysts,
hydrogen break combines with metals and
non-metals to form corresponding
hydrides.

Hydrogenation
1. hydrogen react with various organic
compounds to give useful, commercially
important products.
2. The reaction in which hydrogen gas reacts
with unsaturated organic compounds in
the presence of a catalyst to form
hydrogenated (saturated) compounds is
called hydrogenation. Eg.
Veg. oil + H2 ⎯⎯⎯⎯⎯→ Solid fat
Unsaturated Vanaspati ghee
Ni 450K
8-10 atm
Oil to soild fat conversion called hardening of oil.

Uses or Applicatoin of H2
1. The manufacture of vanaspati fat (ghee).
2. The synthesis of ammonia, by Haber’s
process.
3. The manufacture of methanol, hydrogen
chloride and metal hydrides.
4. fuel cells, for generating electrical energy.
5. metallurgy, to reduce heavy metal oxides to
metals.
6. Atomic hydrogen or oxyhydrogen torches.
7. Rocket fuel (mixt. of liquid H2 and liq. O2).

Atomic hydrogen or oxyhydrogen torche
1. For cutting and welding of metals, very high
temperature is required.
2. Atomic hydrogen is produced when
molecular hydrogen (dihydrogen gas) at
atmospheric pressure is passed through an
electric arc struck between two tungsten
electrodes at 3773−4273 K.
H2 ⎯⎯⎯⎯⎯→ 2H ∆H =435.90kJ mol−1
Molecular Atomic
hydrogen hydrogen
Electricarc 3773 4273K

Atomic hydrogen or oxyhydrogen torche
3. This produce product atomic hydrogen
have a very short life time of 0.3 seconds
and are extremely reactive.
4. The atomic hydrogen atoms get
immediately converted into molecular
form and during this conversion, large
amount of energy is liberated.
5. Thus, atomic hydrogen or oxy-
hydrogen torches are used for cutting
and welding purposes.

Hydride
1. Dihydrogen combines with
elements (except noble gases) to
form binary compounds, called
hydrides.
2. General formula- EHx
Where E= element, x= no. of H
atom
3. Example- LiH, MgH2, B2H6 etc.

Covalent hydride
Most of the P-block element form covalent hydride.
They are volatile compound.
Eg. H2O, CH4, NH3, HF etc

Electron deficient
hydride
Those hydride in
which central atom
has less then 8
electron in the
outermost shell.
Group 13 element
Act as a lewis acid-
e- accepter.
Eg. B2H6 diborane
Electron precis
hydride
Those hydride in
which central
atom have 8
electron in the
outermost shell.
Group 14 element
Netural
Eg. CH4 methane
Electron rich
hydride
Those hydride in
which central atom
has more then lone
pair electron in the
outermost shell.
Group 15,17 element
Act as a lewis base
e- donor.
Eg. NH3- 1, H2O-2
lone pair e-
Classification of molecule hydride-

Example
Hydrolysis-
Na2CO3 + 2H2O ⎯→ 2NaOH + H2CO3
Salt Base Acid
Hydration
CuSO4(s) + 5H2O(l) ⎯→ CuSO4.5H2O(s)
Salt Hydrated salt
(Colourless) (Blue)

Hydrogen 2017

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Hydrogen 2017

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