Hydrogen, Oxygen and Water

1. Hydrogen, Oxygen and Water Chapter 18 Dr Ayesha Mohy-ud-din

2. Hydrogen Chemistry Hydrogen: Greek- hydro-water and genes-forming 11.0079H The lightest element and has only proton and one electron and it has no neutron. All other elements were originally made from hydrogen atoms or other elements that were originally made from hydrogen atoms.

3. Hydrogen History • 1671 - Robert Boyle dissolved iron fillings in dilute hydrochloric acid and reported that the ‘fumes’ given off were highly flammable. • 1766 - Discovered and isolated by Henry Cavendish in 1766. 1781-H2+O2+ ED → H2O • 1781 – Named Hydrogen by Antoine Lavoisier. • 1789- van Troostwijk & Deiman-Electrolysis of water- • 1898 - James Dewar produced the first liquid hydrogen. • 1900 - the first ‘Zeppelin =Airship’ made its flight filled with hydrogen. • 1909-The pH scale by P. L. Sørensen • 1923-J. N. Brønsted defined an acid as a proton donor. • 1931 - Harold Urey discovered deuterium. • 1947-LiAlH4 prepared by H. I. Schlesinger-Chicago University • 1954-Detonation of H-Bomb on Bikini Atoll • 1960’s Super acid (BF3-HF)G. A. Olah.. Nobel 1994 • 1978- H. C. Brown Nobel Prize, Purdue University, Hydroboration • 1984-First Stable T.M. dihydrogen compound discoved by G. Kubas • 1996 - Metallic hydrogen was prepared Hindenburg 1937 H-Bomb 1952 1900-1930’s German war machine 1891 water splitting Poul la Cour -Danish

4. Why Hydrogen? Hydrogen is a Part of Life H2O , NH3, MeOH …. The first hydrogen refueling station Reykjavík, Iceland in April 2003. DaimlerChrysler fuel cell buses went into public use in nine cities across the European Union in 2004. Hydrogen Economy

5. Some Uses Hydrogen • Selected uses of hydrogen: • Food ... to hydrogenate liquid oils (e.g. soybean, fish, cottonseed and corn) converting them to semisolid materials such as shortenings, margarine and peanut butter. • Chemical processing ... primarily to manufacture ammonia (nitrogen fixation), hydrochloric acid and methanol, but also to hydrogenate non-edible oils for soaps, insulation, plastics, ointments and other specialty chemicals. • Metal production and fabrication ... to serve as a protective atmosphere in high-temperature operations such as stainless steel manufacturing; commonly mixed with argon for welding austenitic stainless. Also used to support plasma welding and cutting operations. • Pharmaceuticals ... to produce sorbitol (sugar alcohol) used in cosmetics, adhesives, surfactants, and vitamins A and C. • Aerospace ... to fuel spacecraft, but also to power life-support systems and computers, yielding drinkable water as a by-product. • Electronics ... to create specially controlled atmospheres in the production of semiconductor circuits. • Petroleum Recovery and Refinery ... to enhance performance of petroleum products by removing organic sulfur from crude oil, as well as to convert heavy crude to lighter, easier to refine, and more marketable products. Hydrogen's use in reformulated gas products helps refiners meet Clean Air Act requirements. • Power Generation ... to serve as a heat transfer medium for cooling high speed turbine generators. Also used to react with oxygen in the cooling water system of boiling water nuclear reactors to suppress stress corrosion cracking in the cooling system. • Fuel Cells ... used as a fuel to power fuel cell generators that create electricity through an electrochemical process in combination with oxygen.

6. Occurrence • Hydrogen (hydrogen atoms) is the most abundant element in the universe (90% of all atoms and ¾ of total mass), followed by Helium. • Hydrogen is found in the stars and plays an important role in powering the Universe through interstellarproton-proton reaction* and carbon-nitrogen cycle**. 41H→4He + 2e+ + 2ne Q = 26.72 MeV @ T > 107K Q=Energy evolved (νe is neutrino) 41H + 12C→4He + 12C+ 2e+ + 2ne Q = 26.72 MeV @ T >1.6x107 • Hydrogen is the third (after oxygen and silicon) most abundant element in earth. • Despite its simplicity and abundance, hydrogen doesn't occur naturally as a gas on the Earth—it's always combined with other elements.

7. Hydrogen 11.0079HNuclear spin = ½ Electron Spin = ± ½ Electronic configuration 1s1 (H.) 1s1 - e-→ 1s0 (H+) 1s1 + e-→ 1s2 (H-)

8. Location in the Periodic Table

9. Summary • Despite its position on top of Group I, it is not really part of this group: • It is a gas and not a metal. • It does not react with water. • Far more electronegative than the alkali • Electronegativity is the tendency of an atom in a molecule to attract electrons. • Electronegativity is useful in predicting the general chemical behavior of an element. • In general large difference in electronegativity between two elements leads to the formation of ions and small difference in electronegativity leads to sharing of electrons.

12. Hydrides • Ionic (saltlike) hydrides • when hydrogen combines with very active metals from Group I or Group II • the hydride ion (H-) is a strong reducing agent • ionic hydrides react violently in water: • LiH + H2O --> H2 + Li+ + OH- • Covalent hydrides • when hydrogen combines with other nonmetals, e.g. in HCl, NH3, CH4, and H2O

13. Hydrides • Metallic hydrides • formed when transition metal crystals are treated with hydrogen gas • the hydrogen atoms migrate into the crystal structure to occupy holes or interstices • a solid solution is formed • when these interstitial hydrides are heated, H2 gas is released • use these intersitial hydrides for hydrogen gas storage

14. Covalent Hydrides • The electrons in the bond are shared between M & H. • The electronegativity of the element ~2.1 and varies from ~2.5-1.5. • Bond polarity depends on electronegativity differences between M &H and varies from d+ (e.g. S-H) to d- (e.g. B-H and Ga-H)

15. Hydrides

17. Oxygen Chemistry Oxygen: Greek-oxus or oxys (sharp, acid) and geinomai or genes (former)-acid former 815.9994O 1s22s22p4 The most abundant element in the universe and has eight proton, eight electron and eight neutron. Oxygen is an important component of air, produced by plants during photosynthesis and is necessary for aerobic respiration in animals.

18. History • <1771- prepared by many individuals but were not able to isolate it or recognize it as an element. • In 1770, G.E. Stahl, a German physician - all inflammable objects contained a material substance that he called "phlogiston," from a Greek word meaning "to set on fire." • 1771 Carl Wilhelm Scheele (Swedish pharmacist) discovered Oxygen called it ‘fire air’ was not immediately recognized. • 1772 - Joseph Black (Scottish chemist), and his student, Daniel Rutherford- a living creature gives up phlogiston while breathing and when placed in air that is already saturated with phlogiston, can no longer breathe and must die. • 1774 Joseph Priestley independent discovery & confirmed oxygen. • 1774 Antoine Laurent Lavoisier – oxygen. • 1848 - Faraday while he was investigating the magnetic susceptibility of matter, he discovered that oxygen could be drawn into a magnetic field (paramagnetic). • 1950 - Paul Hersch developed electrochemical oxygen sensor. • Scheele Joseph Priestley Antoine L. Lavoisier Benjamin Franklin Cartoon of Priestley calling for the head Radical Thinker & wife Marie-Ann Paulze (Through a conscious revolution, became the father of modern chemistry)of King George III. (Law degree at the Collège Mazarin)

19. Why Oxygen? • Oxygen is a part of life - supports all life on this planet and is essential to combustion as well as respiration • Photosynthesis Respiration Agriculture Environment • Chemicals, H2O2 Zeolites Electronegativity Electronegativity

20. Oxides • Binary Oxygen compounds are generally referred to as • oxides • With metals the compounds may be • (a) oxides; O2- - oxidation number (–2) • (b) peroxides; O22- - oxidation number (–1) • (c) superoxides; O2- - oxidation number (- ½ ) • Oxides may be acidic, basic, neutral or Amphoteric

21. Selected Uses of Oxygen • Essential for many important industrial and biological processes that may include: • Oxidizer (only fluorine having a higher electronegativity) used in rocket propulsion and manufacturing disinfectant, pharmaceuticals, etc…. • Medicine & Biological life support- Respiration - oxygen supplementation, gas poisoning, and anesthetic when mixed with nitrous oxide, ether vapor, etc.. • Oxygen is essential for life takes part in processes of combustion & respiration. • Oxygen is used in welding. • Metalloragy- melting, mining, refining and manufacture of steel, other metals and manufacture of stone and glass products. • Recreational - mild euphoric, has a history of recreational use often mixed with nitrous oxide to promote a kind of analgesic effect. • Manufacture of chemicals by controlled oxidation

22. Occurrence • Oxygen is the most abundant element in the Universe originated by green-plant photosynthesis. chlorophyl/enzyme H2O + CO2 + hv ↔ O2 + {CH2O} DH = +/- 469 kJmol-1 • Oxygen comprises about 46.7 % of earth’s crust, 87% by weight of the oceans (as H2O) and 20% of the atmosphere of Earth (as O2, molecular oxygen, or O3, ozone). • Oxygen compounds, particularly metal oxides, silicates (SiO44−), and carbonates (CO32−), are commonly found in rocks and soil. • Frozen water is a common solid on the outer planets and comets. The ice caps of Mars are made of frozen carbon dioxide. • Oxygen compounds are found throughout the universe and the spectrum of oxygen is often seen in stars (see carbon-nitrogen-oxygen cycle in 1H-1H fusion.

23. Forms of oxygen • Molecular – O2, O3 and O4 (allotropes) • Atomic- highly reactive • Ionic- oxides O2-, peroxides O22-, superoxides O2-,…. (see group I and II oxides). • Molecular (covalent) compound of oxygen – neutral (e.g. SiO2, OsO4, CO2..) & ionic (e.g. SO42-, CO32-, NO3-, …)

24. Molecular oxygen • Oxygen is a colorless, odorless gas and at standard pressure, oxygen liquefies to a pale blue liquid which boils at -183.0 ºC. Solid oxygen melts at -218.8 ºC. Oxygen is sparingly soluble in water & slightly heavier than air. Liquid O2

25. Industrial Production • Fractional distillation of liquefied air @-183 °C (O2) and @ -196 °C .

26. O2 & Haemoglobin • Active site metalloprophyrin

27. Di-oxygen metal compounds • Metal-dioxygen compounds • http://www.res.titech.ac.jp/~smart/research/subject(e).html • http://www.iuac.org/publications/pac/1995/pdf/6702x0241.pdf

28. Main Group Oxides: Ionic vs Covalent • With the exception of a few Nobel gas elements such as Xe, oxygen forms oxides with all elements in the periodic table. • If D Electronegativity > 1.5 • the oxide is ionic. • If D Electronegativity < 1.5 • the oxide is covalent.

29. Main Group Oxides Increasing covalent & acidic character Increasing ionic & basic character

31. Hydrolysis of goup I & II oxides • M2O+H2O → 2M+ + 2OH- oxides (O2-) • M2O2 +2H2O → 2M+ + 2OH- + H2O2 peroxide (O22-) • 2MO2 +2H2O → O2 + 2M+ +2OH- + H2O2 superoxide (O2-1) M = Group I metal in this case

32. Hydrogen Peroxides • Why Hydrogen Peroxide?

33. Selected Uses of Hydrogen Peroxides • Multipurpose Disinfectant - Kills mold, mildew, fungi, viruses, bacteria and other harmful biological contaminants. • Health – toothpaste, mouthwash, shower, facial … • Agriculture - Sprouting Seeds, House and Garden Plants, Vegetable Soak • Powerful Oxidizer for a variety of organic and inorganic compounds  • "green" bleaching agents for the paper and textile industries. • Wastewater treatment. • Hydrometallurgical processes (for example, the extraction of uranium by oxidation) • Bleaching agent - paper, textile, teeth and hair