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Chemistry of Hydrogen

Chemistry of Hydrogen. Chemistry of Hydrogen ( 1 H). The first element of the periodic table. Atomic Number = 1 Atomic weight = 1.0079 Electronic configuration = 1s 1. Introduction. Isotopes of Hydrogen. Protium / Hydrogen Deuterium Tritium. Isotopes of Hydrogen.

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Chemistry of Hydrogen

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  1. Chemistry of Hydrogen

  2. Chemistry of Hydrogen (1H) The first element of the periodic table. Atomic Number = 1 Atomic weight = 1.0079 Electronic configuration = 1s1

  3. Introduction

  4. Isotopes of Hydrogen Protium / Hydrogen Deuterium Tritium

  5. Isotopes of Hydrogen • Protium / Hydrogen (H) • It is the most commonly available isotope. • It constitutes 99% of total hydrogen available in nature. • The molecule of ordinary hydrogen is diatomic (H2) • The nucleus of atom consist of single proton & no neutron (mass number = 1). • It is represented by .

  6. Isotopes of Hydrogen • Deuterium / Heavy Hydrogen (D) • Deuterium constitutes 0.016% of total hydrogen occurring in nature. • The molecule of deuterium or heavy hydrogen is diatomic D2. • The nucleus of atom consist of single proton & a neutron (mass number = 2). • It is represented by .

  7. Isotopes of Hydrogen • Tritium (T) • It is formed in upper atmosphere by certain nuclear reaction induced by cosmic rays. • It constitutes 1 part in 1021 parts of total hydrogen available in nature. • The molecule of Tritium is diatomic T2. • The nucleus of atom consist of single proton & two neutron (mass number = 3). • It is represented by .

  8. Isotopes of Hydrogen • Tritium (T) • It is radioactive in nature. • Tritium decays by the loss of β particle to yield rare but stable isotope of helium.

  9. Isotopes of Hydrogen • Tritium (T) • It can be obtained by bombarding neutron on isotopes of Lithium.

  10. Importance/ Applications of Isotopes • Use of deuterium & tritium in nuclear energy • In fusion reactor, tritium & deuterium are heated to give a plasma in which the nuclei react to produce a neutron & . • Energy obtained per unit mass of deuterium & tritium nuclei is about 4 times more than that from fission of Uranium & 10 million times more than from petrol.

  11. Nuclear Reaction of Deuterium & Tritium

  12. Importance of Isotopes • Heavy water (D2O): • used as neutron moderator & Coolant for nuclear reactors • Decides reaction mechanism • For synthesis of organic compounds used as solvents in NMR spectroscopy

  13. Importance of Isotopes • Kinetic Isotope effect: • Differences in the properties which arise from the difference in mass are called as isotope effect. • Rates of reactions are measurable different for the process. • The detection of this kinetic isotope effect help to support a proposed reaction mechanism of many chemical reactions.

  14. Importance of Isotopes • Isotope effect in detection of motion of hydrogen: • The heavier isotope (D) results in lower frequency. • This isotope effect can be studied by IR spectra of H & D substituted molecule to determine motion of H atom in the molecule.

  15. Importance of Isotopes • Isotopes as tracers: • The distinct properties of isotopes makes them useful as tracers. • H & D in various reactions by IR & mass spectroscopy. • Tritium can be detected by its radioactivity.

  16. Importance of Isotopes • Use in NMR (Nuclear Magnetic Resonance) Spectroscopy: • 1H-NMR detects the presence of hydrogen nuclei in compound & is powerful method for structure determination of molecule, even like protein.

  17. Importance of Isotopes • Tritium in self powered lighting devices. • Tritium is used in specialized self powered lighting devices. • The emitted electrons from radioactive decay of small amount of tritium cause phosphors (A phosphor, most generally, is a substance that exhibits the phenomenon of luminescence) to glow.

  18. Importance of Isotopes • Tritium in nuclear weapon: • Tritium is used as nuclear weapons to enhance efficiency & yield of fission bombs. • It is used in hydrogen bomb.

  19. Methods of Preparation Laboratory Scale Preparation Industrial Production From Solar Energy

  20. 1. Laboratory Scale Preparation • From Aqueous acid and metal: • Metals like Fe, Zn, Mg , Al react with dilute acids to form hydrogen gas.

  21. 1. Laboratory Scale Preparation • From alkali and metal: • H2 can be prepared in laboratory scale by reaction of Zn, Al or Si with hot alkali solution. Zn + NaOH +H2O NaZnO2 + 3/2 H2

  22. 1. Laboratory Scale Preparation C. Methanol steam reformer: Methanol and steam if passed over Cu, ZnO or Pd catalyst mixture at 250-3500C, it produces hydrogen. CH3OH+H2O Cu, ZnOCO2 + 2 H2 CH3OH+ 1/2 H2O Pd CO2 + 2 H2

  23. 2. Industrial/Commercial Production of H2 A. Steam Reforming of Hydrocarbon (methane): Hydrocarbons such as methane (from natural gas) is mixed with steam & passed over nickel catalyst at 700 – 1100oC to yield water gas (mixture of CO & H2). Further reaction of water gas produces more H2 by water gas shift reaction.

  24. 2. Industrial/Commercial Production of H2 Water Gas Shift Reaction This reaction increases the yield of hydrogen by passing more steam in mixture of CO + H2O at 370 - 400oC in presence of FeO catalyst.

  25. 2. Industrial/Commercial Production of H2 B. Steam Reforming of coke / Coal: Hydrogen is made cheaply & in large amount by passing steam over red hot coke/ coal. The product is water gas . The process takes place at 700-1000oC. To produce more H2, water gas is subjected to water gas shift reaction.

  26. 2. Industrial/Commercial Production of H2 Water Gas Shift Reaction This reaction increases the yield of hydrogen by passing more steam in mixture of CO + H2O at 370 - 400oC in presence of FeO catalyst.

  27. 2. Industrial/Commercial Production of H2 C. Electrolysis of water Acidic medium:

  28. 2. Industrial/Commercial Production of H2 Electrolysis of water At Cathode: At Anode:

  29. 3. From Solar Energy: • Water splitting (thermal Process) • Water splitting is the general term for a chemical reaction in which water is separated into oxygen & hydrogen by solar heat.

  30. Reactions involved • In presence of metal oxides at about 2200oC, water splits into hydrogen and oxygen. • Hydrogen needs to be sepataed from the mixture

  31. Compounds of Hydrogen Molecular hydrides Saline hydrides Metallic hydrides Intermediate hydride

  32. Molecular Hydrides • Hydrocarbons • Methane

  33. Molecular Hydrides • Hydrocarbons • Methane • It is the simplest hydrocarbon. • At room temperature & standard pressure, it is colourless, odorless & flammable gas. • It undergo combustion reaction as • Apart from this combustion reaction, it is not very reactive.

  34. Molecular Hydrides • Hydrocarbons • Methane Preparation • Industrial scale preparation • Methane can be produced by hydrogenating CO2 The process involves reaction of H2 & CO2 at elevated temperature & pressure in the presence of Ni-catalyst to produce methane & water.

  35. Molecular Hydrides • Hydrocarbons • Methane Preparation • Industrial scale preparation • Methane is also side products of hydrogenation of CO It involves collection of chemical reactions that convert the mixture of CO & H2 into hydrocarbons.

  36. Molecular Hydrides • Hydrocarbons • Methane Applications • It is used as domestic & industrial fuel.Methane in the form of compressed natural gas is used as vehicular fuel. It is a clean burning fuel • It is important for electrical generation by burning it as a fuel in a gas turbine or steam engine. • Chemical feedstock – in chemical industries, methane is converted to synthesis gas, a mixture of CO & H2, by steam reforming.

  37. Molecular Hydrides • Hydrocarbons • Ethane

  38. Molecular Hydrides • Hydrocarbons • Ethane • It is aliphatic hydrocarbon. • At STP, it is colourless, odorless gas. • It undergo combustion reaction as • It occurs in traces in earth’s atmosphere & sea.

  39. Molecular Hydrides • Hydrocarbons • Ethane Preparation • Laboratory scale preparation • Ethane can be prepared by electrolysis, In this technique an aqueous solution of acetate salt is electrolyzed. • At anode acetate is oxidized to produce CO2 & methyl radical & highly reactive methyl radicals combine to produce ethane.

  40. Molecular Hydrides • Hydrocarbons • Ethane Preparation

  41. Molecular Hydrides • Hydrocarbons • Ethane Applications • It is mainly used in chemical industries in the production of ethylene. It is a raw material for polymer formation. • It can be used as a refrigerant in cryogenic refrigeration system. • In scientific research, liquid ethane is used in cryo-electron microscopy.

  42. Molecular Hydrides • Silane

  43. Molecular Hydrides • Silane (SiH4) • Si:At No. 14: 1S2 2S2 2P6 3S2 3Px1 3Py1 3Pz0 • Group 14 element • Silane has tetrahedral structure (tetravalent) • SP3 hybridized

  44. Molecular Hydrides • Silane • Preparation • Laboratory scale preparation • Silane can be prepared by heating sand with Mg-powder to produce Mg-silica which is then poured into 20% non-aqueous solution of HCl to produce silane.

  45. Molecular Hydrides • Silane • Preparation • Laboratory scale preparation • Silane can be prepared by reducing SiCl4 with LiAlH4, the method gives better yield.

  46. Molecular Hydrides • Silane • Preparation • Industrial Scale Preparation • Commercially silane is prepared by the reaction of SiO2 with Al under high pressure of hydrogen in a molten salt mixture of NaCl & AlCl3

  47. Molecular Hydrides • Silane • Preparation • Industrial Scale Preparation • It can also be prepared by the reaction of LiH with silicon tetrachloride.

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