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All other elements were originally made from hydrogen atoms or other elements that were originally made from hydrogen atoms.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All other elements were originally made from hydrogen atoms or other elements that were originally made from hydrogen atoms.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