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Author Topic: which element comes high flammable after hydrogen ?  (Read 5474 times)

Offline taregg

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which element comes high flammable after hydrogen..........?


 

Offline Bored chemist

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which element comes high flammable after hydrogen ?
« Reply #1 on: 23/10/2011 15:30:28 »
Probably Cs or P. Why do you ask?
 

Offline CliffordK

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which element comes high flammable after hydrogen ?
« Reply #2 on: 23/10/2011 17:34:11 »
Are you talking about in order in the periodic table?
Or oxidation energy?

Lithium? 
Sodium?

Even some metals such as aluminum can undergo violent oxidation given the right conditions.
 

Offline damocles

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which element comes high flammable after hydrogen ?
« Reply #3 on: 25/10/2011 04:15:32 »
As I mentioned in another thread, flammability is a simple switch concept. Something can be flammable, or it can be non-flammable.

As I also mentioned, there are several possible alternatives for introducing a hierarchy. Here is the ordering of some elements relative to hydrogen on 3 of them:

(1) Auto-Ignition Temperature (data from http://www.engineeringtoolbox.com/fuels-ignition-temperatures-d_171.html)

White phosphorus 49C
Red phosphorus 260C
Sulfur 243C
Carbon as charcoal 349C
Carbon as coke/graphite 700C
Hydrogen gas 500C

Unfortunately none of the reactive metals are listed in that table.

(2) Heat (Enthalpy) of combustion per mole at 25C (Data deduced from Housecroft & Constable "Chemistry" 3rd Edition, Appendix 11)

Hydrogen gas   286 kJ (molecule) or 143 kJ (atom)
Coke/graphite    394 kJ (atom)
(Red) Phosphorus     2984 kJ (molecule) or 746 kJ (atom)
Sulfur    2375 kJ (molecule) or 297 kJ (atom)
Lithium   299 kJ (atom)
Magnesium   602 kJ (atom)
Aluminium   838 kJ (atom)
Beryllium   609 (atom)

(3) Heat (Enthalpy) of combustion per gram at 25C (Same source, recalculated for mass basis)

Hydrogen gas   142 kJ/g
Beryllium   67.5 kJ/g
Lithium   43 kJ/g
Coke/graphite   33 kJ/g
Aluminium   31 kJ/g
Magnesium   25 kJ/g
Red Phosphorus   24 kJ/g
Sulfur   9.5 kJ/g

There are many other possible ways of building a league table, but documentation on flash points, or minimum oxygen pressure for sustainable reaction, or flame temperature is much harder to find.

The only table that has hydrogen gas as a clear winner is the heat of reaction per gram, and on that table the element beryllium is a clear second. None of the elements missing from the list above can compete.

However, this particular table would usually be described as "fuel value" rather than "flammability", and it clearly does not mean anything like what we usually mean in everyday language when we talk about "flammability", let alone correspond with scientific usage of the term.



 

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which element comes high flammable after hydrogen ?
« Reply #3 on: 25/10/2011 04:15:32 »

 

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