ppt on hydrogen for class XI th chemistry

INTRODUCTION
▪ Hydrogen, chemical element that exists as a gas at
room temperature. When hydrogen gas burns in air, it
forms water. French chemist Antoine Lavoisier named
hydrogen from the Greek words for “water former.”
▪ Hydrogen has the smallest atoms of any element. A
hydrogen atom contains one proton, and only one
electron . The proton is the center, or nucleus, of the
hydrogen atom, and the electron travels around the
nucleus.
▪ Pure hydrogen exists as hydrogen gas, in which pairs of
hydrogen atoms bond together to make molecules.

Introduction to hydrogen (video)

HOW WAS HYDRGOEN FOUND
▪ Discovered by Henry Cavendish
▪ Hydrogen was discovered in London
▪ It was discovered in the year of 1766

The hydrogen atom
consisting the proton
in the centre or the
nucleus of the hydro-
gen atom and the ele-
ctron travelling aroun-
d the nucleus.

POSITION IN THE PERIODIC TABLE
▪ Hydrogen is the first element in the periodic table of
the elements and is represented by the symbol H.
▪ Hydrogen, with only one proton, is the simplest
element. It is usually placed in Period 1 and Group 1
of the periodic table.
▪ Hydrogen can combine chemically with almost every
other element and forms more compounds than does
any other element. These compounds include water,
minerals, and hydrocarbons—compounds made of
hydrogen and carbon—such as petroleum and natural
gas.

Position of hydrogen in the periodic table

How is Hydrogen Produced?
▪ Reforming fossil fuels
▫ Heat hydrocarbons with steam
▫ Produce H2 and CO
▪ Electrolysis of water
▫ Use electricity to split water into O2 and H2
▪ High Temperature Electrolysis
▫ Experimental
▪ Biological processes
▫ Very common in nature
▫ Experimental in laboratories

STEAM REFORMING
▪ From any hydrocarbon
▫ Natural gas typically used
▪ Water (steam) and hydrocarbon mixed at high
temperature (700–1100 °C)
▫ Steam (H2O) reacts with methane (CH4)
▫ CH4 + H2O → CO + 3 H2 - 191.7 kJ/mol
▪ The thermodynamic efficiency comparable to (or
worse than) an internal combustion engine
▫ Difficult to motivate investment in technology

CARBON MONOXIDE REFORMING
▪ Additional hydrogen can be recovered using
carbon monoxide (CO)
▫ low-temp (130°C) water gas shift reaction
▫ CO + H2O → CO2 + H2 + 40.4 kJ/mol
▪ Oxygen (O) atom stripped from steam
▫ Oxidizes the carbon (C)
▫ Liberates hydrogen bound to C and O2

Hydrogen Steam Reforming Plants

Renewable Energy for Electrolysis
http://www.howstuffworks.com/hydrogen-economy4.htm

High Temperature Electrolysis
▪ Electrolysis at high temperatures
▪ Use less energy to split water

Biological H2 Creation
▪Nature has very simple
methods to split water
▪Scientists are working to
mimic these processes in
the lab; then commercially

PHYSICAL PROPERTIES OF H2
➢Dihydrogen is a :
➢Colourless ,
➢Odourless
➢Tasteless
➢Combustible gas
➢Lighter than air
➢Insoluble in water
➢It’s melting point – 18.73 K
& boiling point – 23.67 K

CHEMICAL PROPERTIES OF H2
▪ Hydrogen gas does not usually react with other chemicals at
room temperature, because the bond between the hydrogen
atoms is very strong and can only be broken with a large
amount of energy.
▪ Since its orbital is incomplete with 1s1 electronic
configuration, it does combine with almost all the elements
.
It accomplishes reactions by:
1.loss of one e- to give H+
2.gain of an e- to form H-
3.sharing electrons to form a single covalent bond.

Bosch reaction
Hydrogenation
Dehydrogenation
Transfer hydrogenation
Hydrogenolysis

BOSCH REACTION
The Bosch reaction is a chemical reaction between carbon
dioxide and hydrogen that produces elemental carbon (graphite), water and
a 10% return of invested heat. This reaction requires the introduction of
iron as a catalyst and requires a temperature level of 530-730 degrees
Celsius.
The overall reaction is as follows:
CO2(g) + 2 H2(g) → C(s) + 2 H2O(g)
The above reaction is actually the result of two reactions. The first
reaction, the reverse water gas shift reaction, is a fast one.
CO2 + H2 → CO + H2O
The second reaction controls the reaction rate.
CO + H2 → C + H2O

The overall reaction produces 2.3×103 joules for every gram of
carbon produced at 650 °C. Reaction temperatures are in the range
of 450 to 600 °C.
The reaction can be accelerated in the presence of
an iron, cobalt or nickel catalyst. Ruthenium also serves to speed
up the reaction.
Together with the Sabatier reaction the Bosch reaction is
studied as a way to remove carbon dioxide and to generate clean
water aboard a space station
The reaction is also used to produce graphite
for radiocarbon dating with Accelerator Mass Spectrometry.
It is named after the German chemist Carl Bosch.

Because of the importance of hydrogen, many related reactions
have been developed for its use. Most hydrogenations use gaseous
hydrogen (H2), but some involve the alternative sources of hydrogen, not
H2: these processes are called transfer hydrogenations. The reverse
reaction, removal of hydrogen from a molecule, is called dehydrogenation.
Hydrogenation
To treat with hydrogen - is a chemical reaction between
molecular hydrogen (H2) and another compound or element, usually in
the presence of a catalyst. The process is commonly employed
to reduce or saturate organic compounds. Hydrogenation typically
constitutes the addition of pairs of hydrogen atoms to a molecule,
generally an alkene. Catalysts are required for the reaction to be usable;
non-catalytic hydrogenation takes place only at very high
temperatures. Hydrogen adds to double and triple bonds in hydrocarbons

A reaction where bonds are broken while hydrogen is added is
called hydrogenolysis, a reaction that may occur to carbon-carbon and
carbon-heteroatom (oxygen, nitrogen or halogen) bonds. Hydrogenation
differs from protonation or hydride addition: in hydrogenation, the
products have the same charge as the reactants.
An illustrative example of a hydrogenation reaction is the
addition of hydrogen to maleic acid to form succinic acid. Numerous
important applications of this petrochemical are found in pharmaceutical
and food industries. Hydrogenation of unsaturated
fats produces saturated fats and, in some cases, trans fats.

DEHYDROGENATION
Dehydrogenation is a chemical reaction that involves the
removal of hydrogen from a molecule as (H2). It is the reverse process
of hydrogenation. Dehydrogenation reactions may be either large scale
industrial processes or smaller scale laboratory procedures.
Classes of the reaction
There are a variety of classes of dehydrogenations:
•Aromatization — Six-membered alicyclic rings can be aromatized
in the presence of hydrogenation catalysts, the elements sulfur
and selenium, or quinones (such as DDQ).
•Oxidation — The conversion
of alcohols to ketones or aldehydes can be effected by metal catalysts
such as copper chromite. In the Oppenauer oxidation, hydrogen is
transferred from one alcohol to another to bring about the oxidation.

•Dehydrogenation of amines — amines can be converted
to nitriles using a variety of reagents, such as Iodine
pentafluoride (IF5).
•Dehydrogenation of paraffin's and olefins — paraffin's like n-
pentane and isopentane can be converted
to pentene and isoprene using chromium (III) oxide as a catalyst at
500 degree C.
Dehydrogenation converts saturated fats to unsaturated fats.
Enzymes that catalyze dehydrogenation are called dehydrogenases.
Dehydrogenation processes are used extensively to produce styrene in
the fine chemicals, oleochemicals, petrochemicals, and detergents
industries.

TRANSFER HYDROGENATION
Is the addition of hydrogen (H2; dihydrogen
in inorganic and organometallic chemistry) to a molecule from a source other
than gaseous H2. It is applied in industry and in organic synthesis, in part
because of the inconvenience and expense of using gaseous H2. One large scale
application of transfer hydrogenation is coal liquefaction using "donor solvents"
such as tetralin
HYDROGENOLYSIS
Hydrogenolysis is a chemical reaction whereby a carbon–carbon or
carbon–heteroatom single bond is cleaved or undergoes "lysis" by
hydrogen. The heteroatom may vary, but it usually is oxygen, nitrogen, or
sulfur. A related reaction is hydrogenation, where hydrogen is added to the
molecule, without cleaving bonds. Usually hydrogenolysis is conducted
catalytically using hydrogen gas.

HYDROGEN STORAGE OPTIONS
REVERSIBLE
HYBRID
TANKS
LIQUID
HYDROGEN
COMPRESSED
GAS
PHYSICAL STORAGE
Molecular
H2
REVERSIBLE
CHEMICAL STORAGE
Dissociative
H2 → 2 H
COMPLEX METAL
HYDRIDES
CONVENTIONAL
METAL HYDRIDES
LIGHT ELEMENT
SYSTEMS
NON-REVERSIBLE
REFORMED FUEL
DECOMPOSED
FUEL
HYDROLYZED FUEL

Compressed Storage
▪ Prototype vehicle tanks developed
▪ Efficient high-volume manufacturing
processes needed
▪ Less expensive materials desired
▫ carbon fiber
▫ binder
▪ Evaluation of engineering factors
related to safety required
▫ understanding of failure
processes

Liquid Storage
▪ Prototype vehicle tanks developed
▪ Reduced mass and especially volume needed
▪ Reduced cost and development of high-volume production processes
needed
• Extend dormancy (time to start
of “boil off” loss) without
increasing cost, mass, volume
• Improve energy efficiency of
liquefaction

Hybrid Physical Storage
▪ Compressed H2 @ cryogenic temperatures
▫ H2 density increases at lower temperatures
▫ further density increase possible through use of
adsorbents – opportunity for new materials
▪ The best of both worlds, or the worst ??
▪ Concepts under development

Non-reversible On-board Storage
▪ On-board reforming of fuels has been rejected as a source of
hydrogen because of packaging and cost
▫ energy station reforming to provide compressed hydrogen is still a
viable option
▪ Hydrolysis hydrides suffer from high heat rejection on-board
and large energy requirements for recycle
▪ On-board decomposition of specialty fuels is a real option
▫ need desirable recycle process
▫ engineering for minimum cost and ease of use

Reversible On-board Storage
▪ Reversible, solid state, on-board storage is the ultimate goal for
automotive applications
▪ Accurate, fast computational techniques needed to scan new
formulations and new classes of hydrides
▪ Thermodynamics of hydride systems can be “tuned” to improve
system performance
▫ storage capacity
▫ temperature of hydrogen release
▫ kinetics/speed of hydrogen refueling
▪ Catalysts and additives may also improve storage
characteristics

ISOTOPES OF
HYDROGEN
Hydrogen has three naturally
occurring isotopes,
denoted 1H, 2H and 3H. Other,
highly unstable nuclei (4H to 7H)
have been synthesized in the
laboratory but not observed in
nature

1H is the most common hydrogen isotope with
an abundance of more than 99.98%. Because
the nucleus of this isotope consists of only a
single proton, it is given the descriptive but
rarely used formal name protium.
1H

2H, the other stable hydrogen isotope, is known as deuterium and
contains one proton and one neutron in its nucleus. Essentially all
deuterium in the universe is thought to have been produced at the
time of the Big Bang, and has endured since that time. Deuterium
is not radioactive, and does not represent a significant toxicity
hazard. Water enriched in molecules that include deuterium
instead of normal hydrogen is called heavy water. Deuterium and
its compounds are used as a non-radioactive label in chemical
experiments and in solvents for 1H-NMR spectroscopy. Heavy
water is used as a neutron moderator and coolant for nuclear
reactors. Deuterium is also a potential fuel for
commercial nuclear fusion
2H

3H is known as tritium and contains one proton and two
neutrons in its nucleus. It is radioactive, decaying into helium-
3 through beta decay with a half-life of 12.32 years. It is so
radioactive that it can be used in luminous paint, making it
useful in such things as watches. The glass prevents the small
amount of radiation from getting out. Small amounts of
tritium occur naturally because of the interaction of cosmic
rays with atmospheric gases; tritium has also been released
during nuclear weapons tests. It is used in nuclear fusion
reactions, as a tracer in isotope geochemistry, and specialized
in self-powered lighting devices. Tritium has also been used in
chemical and biological labeling experiments as a radiolabe
3H

4H contains one proton and three neutrons in its nucleus. It
is a highly unstable isotope of hydrogen. It has been
synthesized in the laboratory by bombarding tritium with
fast-moving deuterium nuclei. In this experiment, the
tritium nuclei captured neutrons from the fast-moving
deuterium nucleus. The presence of the hydrogen-4 was
deduced by detecting the emitted protons. Its atomic
mass is 4.02781 ± 0.00011. It decays through neutron
emission with a half-life of (1.39 ± 0.10) × 10−22 seconds.
4H

5H is a highly unstable isotope of hydrogen. The
nucleus consists of a proton and four neutrons.
It has been synthesized in the laboratory by
bombarding tritium with fast-moving tritium
nuclei. In this experiment, one tritium nucleus
captures two neutrons from the other, becoming
a nucleus with one proton and four neutrons.
The remaining proton may be detected, and the
existence of hydrogen-5 deduced. It decays
through double neutron emission and has a half-
life of at least 9.1 × 10−22 seconds.
5H

6H decays through triple neutron
emission and has a half-life of
2.90×10−22 seconds. It consists of 1
proton and 5 neutrons.
6H

7H consists of a proton and six neutrons. It was first
synthesized in 2003 by a group of Russian, Japanese
and French scientists at RIKEN's RI Beam Science
Laboratory by bombarding hydrogen with helium-
8 atoms. In the resulting reaction, the helium-8's
neutrons were donated to the hydrogen's nucleus.
The two remaining protons were detected by the
"RIKEN telescope", a device composed of several
layers of sensors, positioned behind the target of the
RI Beam cyclotron.
7H

Hydrogen is the only element that has different names
for its isotopes in common use today. During the early study of
radioactivity, various heavy radioactive isotopes were given
their own names, but such names are no longer used, except for
deuterium and tritium. The symbols D and T (instead
of2H and 3H) are sometimes used for deuterium and tritium,
but the corresponding symbol for protium, P, is already in use
for phosphorus and thus is not available for protium. In
its nomenclatural guidelines, the International Union of Pure
and Applied Chemistry allows any of D, T, 2H, and 3H to be
used, although 2H and 3H are preferred.
IMPORTANT

Table:- Atomic And Physical Properties Of Isotopes Hydrogen
Property Hydrogen Deuterium Tritium
Active (%)
Abundance
99.985 0.0156 -15
10
Relative at mass 1.008 2.014 3.016
Melting point 13.96 18.73 20.62
Boiling point 20.39 23.67 25.0
Density 0.09 0.18 0.27
E of fusion 0.117 0.197 _
E of vaporization 0.904 0.197 _
E of dissociation 435.88 443.35 _
Interneuclar dist 74.14 74.14 _
Electronic gain e -73 _ _
Covalent radius 37 _ _
Ionic radius 208 _ _

USES OF HYDROGEN
4 ENERGY
SECURITY
4 ECONOMIC
PROSPERITY
4 ENVIRONMENTAL STEWARDSHIP

INTERIOR OF THE SUN
▪ The Sun’s energy is
produced in the core
through nuclear fusion
of hydrogen atoms into
helium. Gases in the
core are about 150
times as dense as water
and reach temperatures
as high as 16 million
degrees C (29 million
degrees F).

Presence of hydrogen in volcanoes and
in our food particles

Cont….
▪ Hydrogen accounts for about 73 percent of the
observed mass of the universe and is the most
common element in the universe.
▪ Hydrogen atoms were the first atoms to form in
the early universe and that the atoms of the other
elements formed later from the hydrogen atoms.
▪ About 90 percent of the atoms in the universe are
hydrogen, about 9 percent are helium, and all the
other elements account for less than 1 percent.

Cont….
▪ Common Molecules:
Many common molecules
contain hydrogen. In these
molecules, butane
contains ten hydrogen
atoms, ammonia contains
three hydrogen atoms, and
water contains two
hydrogen atoms.

HIGH EFFICIENCY
& RELIABILITY
ZERO/NEAR ZERO
EMISSIONS
.
Transportation
Distributed
Generation
Biomass
Hydro
Wind
Solar
Geothermal
Coal
Nuclear
Natural
Gas
Oil
WithCarbonSequestration

Hydrogen Economy (Hydrogen As Fuel)
With advancement of science and technology we realize in
order to make our lives comfortable fossil fuels are depleating
at an alarming rate and will be exhausted 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
• 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.

Transportation
Desired range can be achieved with on-board hydrogen storage (unlike
Battery Electric Vehicle)
Can be used in internal combustion engines
Trains, automobiles, buses, and ships
Buildings
Combined heat, power, and fuel
Reliable energy services for critical applications
Grid independence
Industrial Sector
Already plays an important role as a chemical
Opportunities for additional revenue streams
Flexibility Of Use

Storing & Transporting Hydrogen
▪ Store and Transport as a Gas
▫ Bulky gas
▫ Compressing H2 requires energy
▫ Compressed H2 has far less energy than the same volume of
gasoline
▪ Store and Transport as a Solid
▫ Sodium Borohydride
▫ Calcium Hydride
▫ Lithium Hydride
▫ Sodium Hydride

Hydrogen-Powered Aircraft
Hydrogen powered passenger aircraft with cryogenic tanks along spine of
fuselage. Hydrogen fuel requires about 4 times the volume of standard jet
fuel (kerosene).

While fuel cells do wear
out over time, A PEM fuel
cell in a vehicle should
have a 4,000 hour service
life, while stationary
applications should last
40,000 hours.
Fuel Cell Life

Fuel leak simulation
Hydrogen on left
Gasoline on right
Equivalent energy release
Hydrogen Safety
Hydrogen Gasoline
Three Second
seconds
One minute

Advantages of a Hydrogen Economy
▪ Waste product of burning H2 is water
▪ Elimination of fossil fuel pollution
▪ Elimination of greenhouse gases
▪ Elimination of economic dependence
▪ Distributed production
▪ The stuff of stars

Disadvantages of Hydrogen Economy
▪ Low energy densities
▪ Difficulty in handling, storage, transport
▪ Requires an entirely new infrastructure
▪ Creates CO2 if made from fossil fuels
▪ Low net energy yields
▫ Much energy needed to create hydrogen
▪ Possible environmental problems
▫ Ozone depletion (not proven at this point)

A Vision of a Hydrogen
Future"I believe that water will one day be employed as fuel, that
hydrogen and oxygen which constitute it, used singly or
together, will furnish an inexhaustible source of heat and
light, of an intensity of which coal is not capable. I believe
then that when the deposits of coal are exhausted, we shall
heat and warm ourselves with water. Water will be the coal
of the future."
Jules Vernes (1870) L´île mystérieuse

HYDROGEN DAMAGE
Hydrogen damage is the generic name given to a large number
of metal degradation processes due to interaction with hydrogen.
Hydrogen is present practically everywhere, several kilometers above the
earth and inside the earth. Engineering materials are exposed to hydrogen and
they may interact with it resulting in various kinds of structural damage.
Damaging effects of hydrogen in metallic materials have been known since
1875 when W. H. Johnson reported “some remarkable changes produced
in iron by the action of hydrogen and acids”. During the intervening years
many similar effects have been observed in different structural materials,
such as steel, aluminum, titanium, and zirconium. Because of the
technological importance of hydrogen damage, many people explored the
nature, causes and control measures of hydrogen related degradation of
metals. Hardening, embrittlement and internal damage are the main hydrogen
damage processes in metals. This article consists of a classification of
hydrogen damage, brief description of the various processes and their
mechanisms, and some guidelines for the control of hydrogen damage.

▪ Hydrogen embrittlement is the process by which various
metals, most importantly high-strength steel,
become brittle and fracture following exposure
to hydrogen. Hydrogen embrittlement is often the result of
unintentional introduction of hydrogen into susceptible
metals during forming or finishing operations and
increases cracking in the material.
▪ Hydrogen embrittlement is also used to describe the
formation of zircaloy hydride. Use of the term in this
context is common in the nuclear industry.
HYDROGEN EMBRITTLEMENT

HYDROGEN LEAK TESTING
Hydrogen leak testing is the normal way in which
a hydrogen pressure vessel or installation is checked for leaks or flaws. There
are various tests.
The Hydrostatic test, The vessel is filled with a nearly incompressible
liquid - usually water or oil - and examined for leaks or permanent changes in
shape. The test pressure is always considerably more than the operating
pressure to give a margin for safety, typically 150% of the operating pressure.
The Burst test, The vessel is filled with a gas and tested for leaks. The
test pressure is always considerably more than the operating pressure to give
a margin for safety, typically 200% or more of the operating pressure.
The Helium leak test, The leak detection method uses helium (the lightest
inert gas) as a tracer gas and detects it in concentrations as small as one part
in 10 million. The helium is selected primarily because it penetrates small
leaks readily.

Usually a vacuum inside the object is created with an external
pump connected to the instrument.
Alternatively helium can be injected inside the product while the
product itself is enclosed in a vacuum chamber connected to the
instrument. In this case Burst and leakage tests can be combined in
one operation.
The Hydrogen sensor, The object is filled with a mixture of
5% hydrogen/ 95% nitrogen, (below 5.7% hydrogen is non-
flammable (ISO-10156). This is called typically a sniffing test.
The handprobe connected to the microelectronic hydrogen
sensors is used to check the object. An audio signal increases in
proximity of a leak. Detection of leaks go down to 5x10-7 cubic
centimeters per second. Compared to the helium test: hydrogen is
cheaper than helium, no need for a vacuum, the instrument could be
cheaper.

Hydrogen safety covers the safe production,
handling and use of hydrogen. Hydrogen poses unique
challenges due to its ease of leaking, low-energy ignition,
wide range of combustible fuel-air mixtures, buoyancy, and
its ability to embrittle metals that must be accounted for to
ensure safe operation. Liquid hydrogen poses additional
challenges due to its increased density and the extremely
low temperatures needed to keep it in liquid form.
HYDROGEN SAFETY

OCCURRENCE OF DIHYDROGEN
▪ Hydrogen is the tenth most common element on Earth.
Because it is so light, though, hydrogen accounts for
less than 1 percent of Earth's total mass. It is usually
found in compounds. Pure hydrogen gas rarely occurs
in nature, although volcanoes and some oil wells
release small amounts of hydrogen gas.
▪ Hydrogen is in nearly every compound in the human
body. For example, it is in keratin, the main protein
that forms our hair and skin, and in the enzymes that
digest food in our intestines. Hydrogen is in the
molecules in food that provide energy: fats, proteins,
and carbohydrates.

PREPARATION OF DIHYDROGEN
▪ Laboratory preparation of dihydrogen:
1.It is usually prepared by the reaction of granulated
zinc with dilute hydrochloric acid. The chemical
equation for this reaction is the following:
Zn + 2HCl → ZnCl2 + H2
2.It can also be prepared by the reaction of zinc with
aqueous alkali. The chemical equation for this
reaction is the following:
Zn +2NaOH Na2ZnO2 + H2
(Sodium zincate)

Cont….
▪ Commercial production of dihydrogen:
1. Electrolysis of acidified water using platinum
electrodes gives hydrogen.
2 H2O electrolysis 2H2 + O2
This chemical equation shows that two water
molecules (with electricity), form two molecules of
hydrogen gas and one molecule of oxygen gas.
2.High purity (>99.95%) dihydrogen is obtained by
electrolysing warm aqueous barium hydroxide
solution between nickel electrodes.

Commercial production of dihydrogen

Cont….
3. It is obtained as a byproduct in the manufacture of sodium
hydroxide & chlorine by the electrolysis of brine solutions .
The reactions that takes place are:
At anode : 2Cl- Cl2 +2e-
At cathode: 2H2O + 2e- H2 + 2OH-
The overall reaction is
2Na+ + 2Cl- +2H2O
Cl2 + H2 + 2Na+ + 2OH-

Cont….
4. Reaction of steam on hydrocarbons at high temperature in
the presence of catalyst yields hydrogen. e.g.,
CH4 + H2O 1270K CO + 3H2
Ni
▪ The mixture of CO & H2 is called water gas.
▪ It is used for synthesis of methanol & a number of
hydrocarbons, therefore it is called synthesis gas or
‘syngas’.
▪ The production of dihydrogen can be increased by reacting
carbon monoxide with steam in the presence iron chromate
as catalyst.
CO + H2O 673K CO2 + H2
Catalyst
▪ This is called water-gas shift reaction. Carbon dioxide is
removed by scrubbing with sodium arsenite solution.

CHEMISTRY OF
DIHYDROGEN▪ Reaction with halogens:
It reacts with halogens, X2 to give hydrogen halides,
HX,
H2+X2 2HX (X= F, Cl, Br, I)
While the reaction with fluorine occurs even in the
dark, with iodine it requires a catalyst.
▪ Reaction with dioxygen:
It reacts with dioxygen to form water. The reaction is
highly exothermic.
2H2 + O2
catalyst or heating 2H2O ; H = -285.9 kJ
mol-1

Cont….
▪ Reaction with dinitrogen:
With dintrogen it forms ammonia.
3H2 +N2
673K,200atm 2NH3; H=-92.6 kJ mol-1
This is the method for the manufacture of ammonia by Haber
process.
Haber Process:
German chemist and Nobel laureate Fritz Haber developed an
economical method of producing ammonia from air and
seawater. In his process, nitrogen is separated from the other
components of air through distillization. Hydrogen is obtained
from seawater by passing an electric current through the water.
The nitrogen and hydrogen are combined to form ammonia
(NH3).

Cont….
▪ Reaction with metals:
Hydrogen also forms ionic bonds with some metals, at
a high temperature, creating a compound called a
hydride.
H2 +2M 2MH
Where M is an alkali metal (e.g. lithium, sodium,
potassium, rubidium, cesium, and francium.)
▪ Reactions with metal ions & metal oxides:
It reduces some metal ions in aqueous solution &
oxides of metals (less active than iron ) into
corresponding metals.
H2+Pd 2+ Pd + 2H+
yH2 +MxOy xM + yH2O

Cont….
▪ Reactions with organic compounds:
1.Hydrogenation of vegetable oils using nickel as
catalyst gives edible fats. (margarine & vanaspati
ghee).
2.Hydroformylation of olefins yields aldehydes which
further undergo reduction to give alcohols.
H2+CO+RCH=CH2 RCH2CH2CHO
H2 +RCH2CH2CHO RCH2CH2CH2OH

USES OF DIHYDROGEN
▪ The largest use of dihydrogen is in the synthesis of
ammonia which is used in the manufacture of nitric
acid & nitrogenous fertilizers.
▪ Dihydrogen is used in the manufacture of vanaspati
fat.
▪ It is used in the manufacture of bulk organic
chemicals, particularly methanol.
CO + 2H2
catalyst cobalt CH3OH
▪ It is widely used for the manufacture of metal
hydrides.
▪ It is used for the preparation of hydrogen chloride, a
highly useful chemical.

Cont……
▪ In metallurgical processes, it is widely used to
reduce heavy metal oxides to metals.
▪ Atomic hydrogen & oxy-hydrogen torches find use
for cutting & welding purposes.
▪ It is used as a rocket fuel in space research.
▪ Dihydrogen is used in the fuel cells for generating
electrical energy. It has many advantages over the
conventional fossil fuels & electric power.

DIHYDROGEN AS A FUEL:
▪ Dihydrogen releases large quantities of heat on
combustion.
▪ Dihydrogen can release more energy than petrol's.
▪ HYDROGEN ECONOMY: The basic principle of
hydrogen economy is the transportation & storage of
energy in the form of liquid or gaseous dihydrogen.
▪ Energy is transmitted in the form of dihydrogen & not
as electric power.
▪ It is also use in fuel cell for generation of electric
power.

HYDRIDES
▪ Dihydrogen also forms ionic bonds with some metals,
at a high temperature, creating a compound called a
hydride.
▪ If E is the symbol of an element then hydride can be
expressed as EHX (e.g. MgH2) or EmHn (e.g. B2H6).
▪ The hydrides are classified into three categories:
1.Ionic or saline or saltlike hydrides.
2.Covalent or molecular hydrides.
3.Metallic or non-stoichiometric hydrides.

Nearly all elements are able to form hydride
compound

IONIC OR SALINE HYDRIDES
▪ These are stoichiometric compounds of dihydrogen
formed with most of the s-block elements which are
highly electropositive in character.
▪ Covalent character is found in the lighter metal hydrides
(e.g. LiH, BeH2 & MgH2).
▪ The ionic hydrides are crystalline, non-volatile & non-
conducting in solid state.
▪ Their melts conduct electricity & on electrolysis liberate
dihydrogen gas at anode, which confirms the existence of
H-ion.
2H-(melt) anode H2+2e-
▪ Saline hydrides react violently with water producing
dihydrogen gas .
NaH + H2O NaOH + H2

COVALENT OR MOLECULAR
HYDRIDE▪ Dihydrogen forms molecular compounds with most of
the p-block elements. For e.g. CH4, NH3, H2O & HF.
▪ Hydrogen compounds of non metals have also been
considered as hydrides. Being covalent they are volatile
compounds.
▪ Molecular hydrides are further classified according to the
relative number of electrons & bonds in their Lewis
structure into:
1.Electron-deficient
2.Electron-precise
3.Electron-rich hydrides.

ELECTRON-
DEFICIENT
HYDRIDES
ELECTRON-PRECISE
HYDRIDES
ELECTRON-RICH
HYDRIDES
Has few electrons for
Lewis structure.
Elements of group 13
forms these
compounds.
For e.g. Diborane
(B2H6).
They act as Lewis
acids i.e. electron
acceptor.
Have the required
number of electrons
for Lewis structure.
Elements of group 14
forms these
compounds.
For e.g. CH4.
Have excess electrons
which are present as
lone pair.
Electrons of group 15-
17 forms such
compounds.
For e.g.NH3-
has1lonepair, H2O-
has 2 lone pairs.
They act as Lewis
bases i.e. electron
donor.

METALLIC HYDRIDES
▪ These are formed by many d-block & f-block elements.
▪ The metals of group 7,8 & 9 do not form hydride.
▪ These hydrides conduct heat & electricity though not as
efficiently as their parent metals do.
▪ Unlike saline hydrides, they are almost non-stoichiometric,
being deficient in hydrogen. For e.g. LaH2.87 & YbH2.55.
▪ Law of constant composition does not hold good.
▪ The property of absorption of hydrogen on transition metal
is widely used in catalytic reduction/hydrogenation
reactions for the preparation of large number of compounds.
▪ Some of the metals can accommodate a very large volume
of hydrogen & can be used as its storage media.

Water
▪ A major part of all living organisms is made up of
water.
▪ Human body has about 65% & some plants have as
much as 95% water.
▪ It is a crucial compound for the survival of all life
forms.
▪ It is a solvent of great importance.

Physical properties of water
▪ It is a colourless & tasteless liquid.
▪ The unusual properties of water in the condensed
phase (liquid & solid) are due to the presence of
extensive hydrogen bonding between water molecules.
▪ Water has a higher specific heat, thermal conductivity,
surface tension, dipole moment & dielectric constant
when compared to other liquids.
▪ It is an excellent solvent for transportation of ions &
molecules required for plant & animal metabolism.
▪ Due to hydrogen bonding with polar molecules, even
covalent compounds like alcohol & carbohydrates
dissolve in water.

STRUCTURE OF WATER
▪ In the gas phase water is a bent molecule with a bond angle of
104.50 ,
and O-H bond length of 95.7 pm.
▪ It is a highly polar molecule .
▪ In the liquid phase water molecules are associated together by
hydrogen bonds.
▪ Density of water is more than that of ice.

Hydrogen Bonding in Water:
Hydrogen bonds are chemical bonds that form between
molecules containing a hydrogen atom bonded to a strongly
electronegative atom . Because the electronegative atom
pulls the electron from the hydrogen atom, the atoms form
a very polar molecule, meaning one end is negatively
charged and the other end is positively charged. Hydrogen
bonds form between these molecules because the negative
ends of the molecules are attracted to the positive ends of
other molecules, and vice versa. Hydrogen bonding makes
water form a liquid at room temperature.

STRUCTURE OF ICE:
▪ Ice has a highly ordered three dimensional
hydrogen bonded structure.
▪ Examination of ice crystals with x-rays shows that
each oxygen atom is surrounded tetrahedrally by
four other oxygen atoms a distance of 276pm.
▪ Hydrogen bonding gives ice a rather open type
structure with wide holes. These holes can hold
some other molecules of appropriate size
interstitially.

Chemical properties of water
▪ Amphoteric nature: it has the ability to act as an acid as
well as a base i.e., it behaves as an amphoteric substance.
In the Bronsted sense it acts an acid with NH3 and a base with
H2S.
H2O+ NH3 OH- + NH4
+
H2O+ H2S H3O++ HS-
The auto-protolysis (self- ionization) of water takes place as
follows:
H2O +H2O H3O+ +OH-
acid-1 base-2 acid-2 base-1

REDOX REACTIONS INVOLVING WATER
▪ Water can be easily reduced to dihydrogen by highly
electropositive metals.
2H2O +2Na 2NaOH +H2
Thus ,it is a great source of dihydrogen.
▪ Water is oxidised to O2 during photosynthesis.
6CO2 +12H2O C6H12O6 + 6H2O +6O2
▪ With fluorine also it is oxidised toO2.
2F2 + 2H2O 4H+ + 4F- +O2

Hydrolysis reaction
▪ Due to high dielectric constant, it has a very strong
hydrating tendency. It dissolves many ionic
compounds. However, certain covalent& some
ionic compounds are hydrolysed in water.
P4O10 +6H2O 4H3PO4
SiCl4 +2H2O SiO2 + 4HCl
N3- + 3H2O NH3 +3OH-

A hydrolysis process generally involves water

HYDRATES FORMATION
▪ From aqueous solutions many salts can be crystallised
as hydrated salts. Such an association of water is of
different types viz.,
(i) coordinated water e.g.,
[Cr(H2O)6 ]3+ 3Cl-
(ii) interstitial water e.g.,
BaCl2.2H2O
(iii) hydrogen-bonded water e.g.,
[Cu(H2O)4]2+SO4
2-.H2O in CuSO4.5H2O

HYDROGEN PEROXIDE:
▪ Hydrogen peroxide is an important chemical used in pollution
control treatment of domestic & industrial effluents.
PREPARATION:
▪ It can be prepared by the following methods:
1.Acidifying barium peroxide & removing excess water by
evaporation under reduced pressure gives hydrogen peroxide.
BaO2.8H2O+H2SO4 BaSO4+H2O2+8H2O
2.Preoxodisulphate, obtained by electrolytic oxidation of
acidified sulphate solutions at high current density, on
hydrolysis yields hydrogen peroxide.
2HSO4
- electrolysis HO3SOOSO3H hydrolysis 2HSO4
-
+2H++H2O2

Cont….
▪ This method is now used for the laboratory preparation of D2O2.
K2S2O8+2D2O 2KDSO4+D2O2
3.Industially it is prepared by the auto-oxidation of 2-
alklylanthraquinols.
2-ethylanthraquinol H2O2+(oxidised product)
▪ In this case 1% H2O2 is formed. It is extracted with water &
concentrated to 30% (by mass) by distillation under reduced
pressure. It can be further concentrated to 85% by careful
distillation under low pressure. The remaining water can be
frozen out to obtain pure H2O2.

Preparation of hydrogen peroxide

PHYSICAL PROPERTIES:
▪ The pure state H2O2 is an almost
colourless liquid
▪ Meting point - 272.4K.
▪ Boiling point - 423K
▪ Vapour pressure (298K) – 1.9mmHg.
▪ H2O2 is miscible with water in all proportions &
forms a hydrate H2O2.H2O.
▪ A 30% solution of H2O2 is marketed as ‘100V’
hydrogen peroxide. It means that 1ml of 30% H2O2
solution will give 100V of oxygen at STP.
▪ Hydrogen peroxide has a non-planar structure.

CHEMICAL PROPERTIES:
▪ It acts as an oxidising as well as reducing agent in
both acidic & alkaline media.
1.Oxidising action in acidic medium:
2Fe2+ +2H+ +H2O2 2Fe3+ +2H2O
PbS +4H2O2 PbSO4+4H2O
2.Reducing action in acidic medium:
2MnO4
- +6H+ +5H2O2 2Mn2+ +8H2O+5O2
HOCl +H2O2 H3O+ +Cl- +O2

Cont….
3.Oxidising action in basic medium:
2Fe2+ +H2O2 2Fe3+ +2OH-
Mn2+ +H2O2 Mn4+ +2OH-
4.Reducing action in basic medium:
I2+H2O2+2OH- 2I-+2H2O+O2
2MnO4
-+3H2O2 2MnO2+3O2+2H2O+2OH-

STORAGE
▪ H2O2 decomposes slowly on exposure to light.
2H2O2 2H2O+O2
▪ In the presence of metal surfaces or traces of
alkali, the above reaction is catalysed. It is,
therefore stored in wax-lined glass or plastic
vessels in dark.
▪ It is kept away from dust because dust can induce
explosive decomposition of the compound.

USES:
▪ It is used as hair bleach & as a mild disinfectant. As an
antiseptic it is sold in the market as perhydrol.
▪ It is used to manufacture chemicals like sodium
perborate & per-carbonate, which are used in high
quality detergents.
▪ It is used in the synthesis of hydroquinone, tartaric
acid & certain food products & pharmaceuticals etc.
▪ It is employed in the industries as bleaching agent for
textiles, paper pulp, leather, oils, fats etc.
▪ It is also used in environmental chemistry.

HEAVY WATER,D2O
▪ It is extensively used as a moderator in nuclear reactors
& in exchange reactions for the study of reaction
mechanisms.
▪ It can be prepared by exhaustive electrolysis of water or
as a by-product in some fertilizer industries.
▪ PHYSICAL PROPERTIES:
▪ Molecular mass: 20.0276 g/mol.
▪ Melting point: 276.8K.
▪ Boiling point: 374.4K.

Cont…..
▪ The bottom ice cubes were made with heavy
water, which is water that uses deuterium
hydrogen (nucleus with an extra neutron) not
regular hydrogen which has no neutron.

USES:
▪ It is used for the preparation of other deuterium
compounds. For e.g.
CaC2 + 2D2O C2D2 + Ca(OD)2
SO3 + D2O D2SO4
Al4C3 + 12D2O 3CD4 + 4Al(OD)3

PROJECT HYDROGEN SUMMARY:-
1)Hydrogen is the most abundant and simplest element
in the universe.
2)Hydrogen has no elasticity.
3)Hydrogen is flameable.
4)Hydrogen is energy carrier.
5)Hydrogen can be cooled and stored as a liquid.
6)Atomic hydrogen is highly reactive.
7)Nascent hydrogen is very reactive form of hydrogen.

▪ Liquid and compressed hydrogen storage
▫ Technically feasible; in use on prototype vehicles
▫ Focus is on meeting packaging, mass, and cost targets
▫ Both methods fall below energy density goals
▫ Unique vehicle architecture and design could enable efficient
packaging and extended range
▪ Solid state storage
▫ Fundamental discovery and intense development necessary “Idea-
rich” research environment

Thank You
PPT Presented by
Name:-lokesh meena
class :-11th f
roll no :-19

ppt on hydrogen for class XI th chemistry

ppt on hydrogen for class XI th chemistry

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