hydrogen the “ groupless ” element
DESCRIPTION
Hydrogen The “ Groupless ” Element. Hydrogen has three isotopes: 1 H, 99.985%, 2 D, 0.015% and 3 T, ~10 -15 %. D 2 O melts at 3.8 ° C,boils at 101.4 °C and is ~10% denser than H 2 O – hence the name “heavy water”. The main use of D 2 O is to slow down neutrons in nuclear reactors. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Hydrogen The “ Groupless ” Element](https://reader036.vdocuments.mx/reader036/viewer/2022062310/56816583550346895dd82af0/html5/thumbnails/1.jpg)
Hydrogen The “Groupless” Element
Hydrogen has three isotopes: 1H, 99.985%,2D, 0.015% and 3T, ~10-15%.
D2O melts at 3.8 °C,boils at 101.4 °C and is ~10% denser than H2O – hencethe name “heavy water”.
The main use of D2O is to slow down neutrons in nuclear reactors.Approximately 1000 tons of D2O is also being used as part of a neutrinodetector at the Sudbury Neutrino Observatory (SNO) in Ontario.
It slows down chemical reaction involving H+
Useful in determining reaction mechanism in Organic and biochemistry.
It can also be used to determine orientationalDynamics of water. 1
![Page 2: Hydrogen The “ Groupless ” Element](https://reader036.vdocuments.mx/reader036/viewer/2022062310/56816583550346895dd82af0/html5/thumbnails/2.jpg)
Tritium• 3T is used as a radioactive tracer in
medicine and• biochemistry as it emits low energy β
radiation• which does relatively little tissue
damage.
• The commercial value of 3T, however,• is that it is the fuel for the “hydrogen• Bomb” and Fusion Reactors.
• 3T decays to 3He, a rare but very useful isotope. It has a
• Lower boiling point than the common 4He, and used in
• extreme low-temperature apparati for cryogenic physics.
![Page 3: Hydrogen The “ Groupless ” Element](https://reader036.vdocuments.mx/reader036/viewer/2022062310/56816583550346895dd82af0/html5/thumbnails/3.jpg)
PEM FUEL CELL
Fuel Cells
![Page 4: Hydrogen The “ Groupless ” Element](https://reader036.vdocuments.mx/reader036/viewer/2022062310/56816583550346895dd82af0/html5/thumbnails/4.jpg)
Polymer Electrolyte Membrane Fuel Cell Alcohols can be used as fuels in these system. The catalyst and membrane materials are currently being developed
![Page 5: Hydrogen The “ Groupless ” Element](https://reader036.vdocuments.mx/reader036/viewer/2022062310/56816583550346895dd82af0/html5/thumbnails/5.jpg)
Solid Oxide Fuel Cell
![Page 6: Hydrogen The “ Groupless ” Element](https://reader036.vdocuments.mx/reader036/viewer/2022062310/56816583550346895dd82af0/html5/thumbnails/6.jpg)
O2-
AirFuel
Exhauste-
e-
![Page 7: Hydrogen The “ Groupless ” Element](https://reader036.vdocuments.mx/reader036/viewer/2022062310/56816583550346895dd82af0/html5/thumbnails/7.jpg)
Fuel Cells could replace
• Internal combustion engines (ICE)• Gas Motor Combined Heat and Power (CHP)• Mobile generators• Batteries • Power Stations • On-board Electricity Generation
(Auxiliary Power Units, APU)
![Page 8: Hydrogen The “ Groupless ” Element](https://reader036.vdocuments.mx/reader036/viewer/2022062310/56816583550346895dd82af0/html5/thumbnails/8.jpg)
H2 – PEMFC for mobile phone with H2 recharging unit
Direct Methanol Fuel Cell PDA with methanol fuel capsule
Prototype DMFC IBM laptop and DMFC unit
Portable electronic devices
![Page 9: Hydrogen The “ Groupless ” Element](https://reader036.vdocuments.mx/reader036/viewer/2022062310/56816583550346895dd82af0/html5/thumbnails/9.jpg)
Generator Replacements
1 kW portable H2- PEMFC generator
DMFC generator with methanol container
![Page 10: Hydrogen The “ Groupless ” Element](https://reader036.vdocuments.mx/reader036/viewer/2022062310/56816583550346895dd82af0/html5/thumbnails/10.jpg)
Demonstrated
• >3000 miles in 12 days - Range
• 100 mph - Speed/power
• -1 -> 35oC – Operating temperature range
• World Record Fuel efficiency 25 km for 1 g H2.
Fuel Cells for Motive Power in Vehicles
Key Targets• Cost $120/kW• Lifetime, reliability
o A conventional car has fuel efficiency ranging between 7 to 20 km/l (18 to 50 MPG), or 14 to 5 L/100km
o This translates to 6 to 18 m for 1 g of fuelo This is a difference of 1400 to 4000 fold.
![Page 11: Hydrogen The “ Groupless ” Element](https://reader036.vdocuments.mx/reader036/viewer/2022062310/56816583550346895dd82af0/html5/thumbnails/11.jpg)
Domestic CHP Units
System generates domestic electricity needs and provides heating – overall efficiency > 80%
CERES POWER SOFC
![Page 12: Hydrogen The “ Groupless ” Element](https://reader036.vdocuments.mx/reader036/viewer/2022062310/56816583550346895dd82af0/html5/thumbnails/12.jpg)
Power Generation on the Mega Watt Scale
http://www.rolls-royce.com/energy/tech/fuelcells.jsp
Rolls Royce 1 MW SOFC system
Fuel Cell Energy Molten Carbonate0.3 MW system
![Page 13: Hydrogen The “ Groupless ” Element](https://reader036.vdocuments.mx/reader036/viewer/2022062310/56816583550346895dd82af0/html5/thumbnails/13.jpg)
Hydrogen Stands Alone!
• Actually, hydrogen belongs to group 1, but it’s not an alkali metal.
• It behaves like an alkali metal and like a halogen
• Electronegativity of 2.1 which is between Boron at 2, and Carbon at 2.5.
• i.e. more electronegative than the metals and less electronegative than the
• nonmetals.
• As its electron configuration 1s1 it can achieve
a “noble gas” configuration by either gaining losing or sharing an electron:
• As the H – H bond is extremely strong, 436 kJ/mol,
• it is a relatively unreactive molecule.
• Even thermodynamically favoured reactions of
• hydrogen often require a catalyst to break the
• strong H – H bond. Hydrogen does, however,
• react with exothermically with oxygen and with fluorine
![Page 14: Hydrogen The “ Groupless ” Element](https://reader036.vdocuments.mx/reader036/viewer/2022062310/56816583550346895dd82af0/html5/thumbnails/14.jpg)
Catalytic Steam Reformation of hydrocarbons.
• Methane, CH4, (or some organic material) reacts with steam at 900-1000
• °C to give CO and H2. Then CO reacts with more steam at 400-500 °C in
• the presence of catalyst, giving more H2 gas
• The purest hydrogen is obtained from the electrolysis of water, but is
• prohibitively expensive for large-scale production.
• The new fuel??? Alternative to oil?
![Page 15: Hydrogen The “ Groupless ” Element](https://reader036.vdocuments.mx/reader036/viewer/2022062310/56816583550346895dd82af0/html5/thumbnails/15.jpg)
Classes of Hydrogen Compounds• There are three general classes of
hydrogen compounds:• Ionic hydrides in which hydrogen combines with elements from groups
1-2• (except beryllium) to form ionic compounds:
• Metallic hydrides (also called interstitial compounds) in which elements• from groups 3-10 “absorb” hydrogen. The hydrogen atoms fill holes in• the metallic lattice, distorting its structure if enough hydrogen is absorbed.
• Covalent hydrogen compounds in which hydrogen • combines with elements from groups 11-17 (or beryllium) • to form covalent molecules:
![Page 16: Hydrogen The “ Groupless ” Element](https://reader036.vdocuments.mx/reader036/viewer/2022062310/56816583550346895dd82af0/html5/thumbnails/16.jpg)
Ionic Hydrides• Most ionic hydrides have a crystal
structure like NaCl (mono• hydrides) or CaF2 (for dihydrides).
• In this case the cations form the main• lattice as they are typically larger• than the hydride anions:
• Ionic hydrides are strong bases, • reacting with acids (even those as weak• as water):
• Ionic hydrides are typically sold as grey powders
• suspended in mineral oil. The oil protects them
• from reacting with moisture in the air though it
• must be washed off (with solvent) if an accurate
• amount is to be weighed. If an ionic hydride is
• not stored properly, it turns white. What has
• happened?
![Page 17: Hydrogen The “ Groupless ” Element](https://reader036.vdocuments.mx/reader036/viewer/2022062310/56816583550346895dd82af0/html5/thumbnails/17.jpg)
Metallic Hydrides• The hydrogen in metallic hydrides can
act • as either “H+” or “H-”:
• Transition metals are often used as catalysts for reactions in which
• hydrogen is added to a double bond (e.g. hydrogenating vegetable oil to
• make margarine). The hydrogen first reacts with the transition metal to
• make a metallic hydride (more reactive than hydrogen gas).
• The ratio of hydrogen : metal atoms in a metallic hydride is often fractional – not every hole in the lattice contains a hydrogen atom.
![Page 18: Hydrogen The “ Groupless ” Element](https://reader036.vdocuments.mx/reader036/viewer/2022062310/56816583550346895dd82af0/html5/thumbnails/18.jpg)
Covalent Hydrogen Compounds
Most of the “everyday” compounds containing hydrogen are covalent hydrogencompounds.
When hydrogen is covalently bonded to a less electronegative element (likealuminum), it has a partial negative charge and may behave like a hydride.
When hydrogen is covalently bonded to an element with similar electro-negativity (like carbon), it is relatively neutral and tends not to be reactive:
When hydrogen is covalently bonded to a more electronegative element (likeoxygen), it has a partial positive charge and may behave as an acid.