Hydrogen for XI std chemistry

BHUSHAN JAIN &

SEMINAR OF CHEMISTRY FOR YEAR 2012-2013

• FROM

SHAHRUKH PATHAN

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.

HOW WAS HYDRGOEN FOUND

Discovered by Henry Cavendish Hydrogen was discovered in London It was discovered in the year of 1766

The hydrogen atomconsisting the protonin 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

PRODUCTION O

F

HYDROGEN

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)

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 CreationNature has very simple methods to split water

Scientists are working to mimic these processes in the lab; then commercially

PROPERTIES

OF

HYDROGEN

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.

REREACTIONS OF

HYDROGEN

Bosch reactionHydrogenationDehydrogenationTransfer hydrogenationHydrogenolysis

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 + H2OThe 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

STOREAGE

HYDROGEN STORAGE OPTIONS

REVERSIBLE

HYBRIDTANKS

LIQUID HYDROGEN

COMPRESSEDGAS

PHYSICAL STORAGE Molecular

H2

REVERSIBLE

CHEMICAL STORAGE Dissociative

H2 2 H

COMPLEX METAL HYDRIDES

CONVENTIONALMETAL 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 -1510

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

ENERGY SECURITY

ECONOMIC PROSPERITY

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 S

equ

estr

atio

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 SectorAlready 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 simulationHydrogen on leftGasoline on rightEquivalent energy

release

Hydrogen Safety

HydrogenGasoline

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 OF

HYDROGEN

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

DIHYDR

OGEN

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 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.

Various uses of dihydrogen

HYDRIDES

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

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+SO42-.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 W

ATER

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

10TH , 11TH TEXTBOOKS. HYDROGEN REFERENCE BOOK

(BRITISH LIBIRARY). INTERNET :- GOOGLE,YAHOO ETC. INTERNET :- MAPS , STATITICS ,

PHOTOS ETC.

PROJECT HELPERS

GUIDANCE :- HEENA SHAIKH MADAM

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