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Hydrogen, Oxygen and WaterHydrogen, Oxygen and Water
Chapter 18Chapter 18Chapter 18Chapter 18
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All other elements were originally made from hydrogen atoms or other elements that were originally made from hydrogen atoms.
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All other elements were originally made from hydrogen atoms or other elements that were originally made from hydrogen atoms.
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
1891 water splitting Poul la Cour -Danish
1900-1930’s German war machine
Why Hydrogen?Hydrogen is a Part of Life
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.
H2O , NH3, MeOH ….H2O , NH3, MeOH ….
Hydrogen Economy
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.
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 interstellar proton-proton reaction* and carbon-nitrogen cycle**.
41H→4He + 2e+ + 2e Q = 26.72 MeV @ T > 107K Q=Energy evolved (νe is neutrino)
41H + 12C→4He + 12C+ 2e+ + 2e 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.
Hydrogen
11.0079H
Nuclear spin = ½
Electron Spin = ± ½
Electronic configuration 1s1 (H.)1s1 - e- → 1s0 (H+)1s1 + e- → 1s2 (H-)
11.0079H
Nuclear spin = ½
Electron Spin = ± ½
Electronic configuration 1s1 (H.)1s1 - e- → 1s0 (H+)1s1 + e- → 1s2 (H-)
Location in the Periodic Table
11 22 1717 1818
111.0081.008H 1sH 1s11 ↔ ↔ 11
1.0081.008H 1sH 1s11 22He 1sHe 1s22
33Li ….2sLi ….2s11 44BeBe 99F 2sF 2s222p2p77 1010Ne 2sNe 2s22spsp66
1111Na….3sNa….3s11 1212MgMg 1717ClCl
1919K…. 4sK…. 4s11 2020CaCa 3535BrBr
3737Rb …5sRb …5s11 3838SrSr 5353II
5555Cs …6sCs …6s11 5656BaBa 8585AtAt
8787Fr … 7sFr … 7s11 8888RaRa
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.
Selected Selected ElectronegativitieElectronegativities (Pauling s (Pauling Scale)Scale)
FF 4.04.0
ClCl 3.03.0
OO 3.53.5
NN 3.03.0
SS 2.52.5
CC 2.52.5
HH 2.12.1
BB 2.02.0
NaNa 0.90.9
Nuclear PropertiesNuclear Properties
Hydorgen Isotopes*Hydorgen Isotopes*Isotope Isotope SymbolSymbol Natural Natural
Abundance, Abundance, %%
½-life½-life Nuclear SpinNuclear Spin NMR NMR SensitivitySensitivity
Protium**Protium** 11HH 99.98599.985 StableStable ½½ 1.0001.000
Deuterium*Deuterium***, **, ††
1122H, DH, D 0.010.01 StableStable 11 0.00970.0097
TritiumTritium††††11
33H, TH, T 1010-17-17 Radio-active Radio-active
-emitter-emitter††
12.4 year12.4 year
1/21/2 1.211.21
•*Have the largest isotope effect of all elements because of the largest mass differences.*Have the largest isotope effect of all elements because of the largest mass differences.•**The dominant isotope.**The dominant isotope.•*** Natural hydrogen contains ~ 0.002% D.*** Natural hydrogen contains ~ 0.002% D.•††-radiation -radiation 00
-1-1ee
Isotope EffectsIsotope Effects
Hydorgen Isotopes*Hydorgen Isotopes*Isotope Isotope HH22 DD22 HH22OO DD22OO
Boiling Boiling point/point/ooCC
-252.81-252.81 -249.7-249.7 100.00100.00 101.42101.42
Mean Bond Mean Bond Enthalpy Enthalpy (kJmol(kJmol-1-1))
436.0436.0 443.3443.3 463.5463.5 470.9470.9
See See DeuteriumDeuterium and and TritiumTritium Isotopes – synthesis and applications. Isotopes – synthesis and applications.
Major used in spectroscopy as tracers to confirm the presence or absence of Major used in spectroscopy as tracers to confirm the presence or absence of certain isotopes.certain isotopes.
Preparation of Hydrogen
• Reaction of electropositive metals with water• e.g.
– 2 Na + 2 H2O → H2+ 2 Na++ 2 OH-
– Ca + 2 H2O→ H2+ Ca2++ 2 OH-
• In the lab: reaction of Fe or Zn with acids
– Zn + 2 H3O+ → H2+ Zn2++ 2 H2O
Preparation of Hydrogen
– Electrolysis-
2H2O (l) + e`s → 2H2(g) + O2(g) on inert electrode, e.g. Pt electrode
Write balance half-reactions for the electrolysis of water?
Show balanced half-reactions for the electrolysis of water.
2NaCl(l) + 2Hg + e`s → 2NaHg(l) + Cl2(g)
2NaHg (l) +H2O(l) → 2H2(g) + 2Hg(l)
Reactions of Molecular Hydrogen (H2)
• Reaction with O2
H2(g) + O2(g) → N.R
2H2(g) + O2(g) + ED → 2H2O(l)
• Reaction with H2O
H2(g) + H2O(l) → N.R.• Reaction with Halogens
H2(g) + F2(g) → 2HF(g) • Reaction with acids
H2(g) + H+(l) → N.R.
• Reaction with bases
H2(g) + OH-(l) → N.R.
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
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
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 + (e.g. S-H) to - (e.g. B-H and Ga-H)
ElectronegativitElectronegativityy
HH 2.12.1
PP 2.22.2
SS 2.52.5
Hydrides
11 22 1313 1414 1515 1616 1717
LiHLiH BeHBeH22 (BH(BH33))2, ….2, …. CHCH44 NHNH33 HH22OO HFHF
NaNaHH
MgHMgH22 (AlH(AlH33))nn SnHSnH44 PHPH33 HH22SS HClHCl
KHKH CaHCaH22 GaHGaH33 GeHGeH44 AsHAsH33 HH22SeSe HBrHBr
RbRbHH
SrHSrH22 InHInH33 SnHSnH44 SbHSbH33 HH22TeTe HIHI
Ionic Ionic HydrideHydridess
EE++HH--
IonicIonic
EE++HH--
CovaleCovalentnt
E-HE-H
CovaleCovalentnt
HH++EE--
RedRed BlueBlue WhitWhitee
Selected hydrides of p-block elements that contain M-H Selected hydrides of p-block elements that contain M-H
covalent Bondscovalent Bonds*, ***, **
1313 1414 1515 1616 1717
BB22HH66 CCnnHH2n+22n+2 NHNH33 HH22OO HFHF
CCnnHH2n2n
CCnnHH2n-22n-2
(AlH(AlH33))nn SiSinnHH2n+22n+2 (n (n 8) 8) PHPH33 HH22SS HClHCl
PP22HH44 HH22SSnn
GeGennHH2n+2 2n+2 (n (n 9) 9) AsHAsH33 HH22SeSe HBrHBr
SnHSnH44 SbHSbH33 HH22TeTe HIHI
* Polarity varies depending on electronegativity differences of M-* Polarity varies depending on electronegativity differences of M-H bond.H bond.
** Group 13 hydrides are electron deficient-** Group 13 hydrides are electron deficient-
Reaction of Ionic Hydrides with water
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.
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.
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)
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
ElectronegativityElectronegativity
OxidesOxides
• 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
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
Occurrence
• Oxygen is the most abundant element in the Universe originated by green-plant photosynthesis.
chlorophyl/enzyme H2O + CO2 + hv ↔ O2 + {CH2O} H = +/- 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.
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. SO4
2-, CO32-, NO3
-, …)
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
Chemical Synthesis of O2
• From water– Electrolysis (see synthesis of hydrogen).
– Chemical oxidation of water
2H2O + 2Cl2 → 4HCl + O2
• From oxides– Thermal decomposition e.g. 2HgO → 2Hg + O2
2BaO2 → 2 BaO + O2 2KMnO4 → K2MnO4 + MnO2 + O2
– chemical decomposition
e.g. MnO2 + 2H2SO4 → 2MnSO4 + 2H2O + O2
• Catalytic decomposition of peroxides2H2O2 → 2H2O + O2 (MnO2 catalyst)
Industrial Production
• Fractional distillation of liquefied air @-183 °C (O2) and @ -196 °C .
• AirAir
GasGas Volume Volume %%
NN22 78.178.1
OO22 20.920.9
ArAr 0.930.93
COCO22 0.0350.035
O2 & Haemoglobin
• Active site metalloprophyrin
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
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 Electronegativity > 1.5 • the oxide is ionic.• If Electronegativity < 1.5 • the oxide is covalent.
Selected Selected ElectronegativitiElectronegativities (Pauling es (Pauling Scale)Scale)
FF 4.04.0
ClCl 3.03.0
OO 3.53.5
NN 3.03.0
SS 2.52.5
CC 2.52.5
HH 2.12.1
BB 2.02.0
NaNa 0.90.9
Main Group Oxides
11 22 1313 1414 1515 1616 1717
LiLi22OO BeOBeO BB22OO33 COCO22 NN22OO55
NaNa22OO MgOMgO AlAl22OO33 SiOSiO22 PP44OO1010 SOSO33 ClCl22OO77
KK22OO CaOCaO GaGa22OO33 GeOGeO22 AsAs22OO
55
SeOSeO
33
BrBr22OO55
RbRb22OO SrOSrO InIn22OO33 SnOSnO22 SbSb22OO
55
TeOTeO
33
II22OO55
CsCs22OO BaOBaO22 ThTh22OO33 PbOPbO22 BiBi22OO55
Ionic Ionic BasicBasic
AmphtAmphtoericoeric
CovalenCovalentt
AcidicAcidic
RedRed BlueBlue WhiteWhite
Increasing covalent & acidic character
Incr
easi
ng io
nic
& b
asic
cha
ract
er
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
Reaction of Oxides and Superoxides with water
Hydrogen Peroxides
• Why Hydrogen Peroxide?
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
Synthesis of Hydrogen Peroxides• Hydrolysis of Group I and II peroxides
e.g. BaO2 + 2H2O → H2O2 + Ba(OH)2
• Nature – photolysis & acid-base conversion of O3
O3 + H2O → H2O2 + O2 hO3 + HO- → HO2
- + O2 @ high pH
HO2- + H2O → H2O2 + HO-
• Electrolysis – aqueous solutions of sulfuric acids, of potassium bisulfate, or of ammonium bisulfate
2HSO4-(aq) -2e- → HSO3OOSO3H
HSO3OOSO3H + H2O → 2HSO4- + H2O2
Describe the synthesis of D2O2.
Reactions of Hydrogen Peroxide• H2O2 is metastable and decomposes as shown
below
2H2O2 → 2H2O + O2 H0 = -98.2 kJmol-1
G0 = -119.2 kJmol-1
(Heterogeneous (e.g. MnO2, Ag, Au or Pt) and homogenous (e.g. OH-, I-, Cu2+ or Fe3+) enhance decomposition)
H2O2 → 2HO. (in cold, dark – catalyzed at high T and h)
(HO. –highly reactive …. chain reactions )
Determing Formula of Hydrate,x.
1. Get mass of sample.
2. Heat sample up to release water.
3. Get mass again. This will be mass of anhdrous salt; mass of water is found by subtraction.
4. From mass of water and anhdrous salt; determine moles of each.
Determining Formula of Hydrate,x.
5. Determine x in Empirical Formula Hydrate. (_CuSO4 .xH2O)
• X = moles H2O / moles CuSO4
6. Mass % H2O = (mass H2O/ mass unknown hydrate)×100
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