Hydrogen

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

How was hydrogen found(video)

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.

The Hydrogen H2 Molecule

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

Hydrogen Steam Reforming Plants

Electrolysis of Water (H2O)

Electolysis of water (video)

Renewable Energy for Electrolysis

http://www.howstuffworks.com/hydrogen-economy4.htm

Biomass Electrolysis Module

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 REACTIONThe 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.

DEHYDROGENATIONDehydrogenation 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

HYBRIDTANKS

LIQUIDHYDROGEN

COMPRESSEDGAS

PHYSICAL STORAGE Molecular

H2

REVERSIBLE

CHEMICAL STORAGE DissociativeH2 → 2 H

COMPLEX METALHYDRIDES

CONVENTIONALMETAL HYDRIDES

LIGHT ELEMENTSYSTEMS

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 ZEROEMISSIONS

.

Transportation

Distributed

Generation

Biomass

Hydro

Wind

Solar

Geothermal

Coal

Nuclear

Natural

Gas

Oil

Wit

h C

arb

on

Seq

ues

tra

tio

n

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

Transporting Hydrogen

Hydrogen-Powered Autos

Hydrogen-Powered Autos

Hydrogen-Powered Trucks

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).

Hydrogen-Powered Rockets

Guts of a Fuel Cell Vehicle

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

RISKS OFHYDROGEN

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)

Dihydrogen in 3D

Cont….

▪ Commercial production of dihydrogen:

1. Electrolysis of acidified water using platinum electrodes gives hydrogen.

2 H2Oelectrolysis 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 + O2catalyst or heating 2H2O ; H = -285.9 kJ

mol-1

Cont….▪ Reaction with dinitrogen:

With dintrogen it forms ammonia.

3H2 +N2673K,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 + 2H2catalyst 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.

Various uses of dihydrogen

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.

Different uses of water

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.

Structure of ice

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

HYDROGENPEROXIDE

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.

Production of Hard water

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

1

Thank YouPPT Presented by

Name:-lokesh meena

class :-11th f

roll no :-19